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Final Answers
© 2000-2024   Gérard P. Michon, Ph.D.

 Andre Dunican Philidor 
1726-1795

Chess

The hardest thing in chess is to win a won game.
Frank Marshall   (1877-1944) 
 Michon
 
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Chess notation (2021-09-21).
FIDE  Laws of Chess (2018)  annotated in red by the  CAA (UK).
 
Guinness Chess Records.
 
The 10 best places to play chess online  by  Chess Strategy Online.
 
Play chess against yourself.
Play chess online  (free, no registration).
Caissa's Web :  free online chess server.
 
Nalimov Tablebase Server  at  Lokasoft 
Chess Endgame Training   |   Endgame Tablebases Online  by  Kirill Kryukov.
History of Chess:  Earliest Chess Books and References   by  Bill Wall.
Combinative Chess  by  Sarah Beth  (Chess.com, 2015-10-19).
Chess Page  by  Timothy J. Thompson (1993).
Chess Page  by  Thane E. Plambeck (c.1963-).
Medieval European Chess.
Mathematicians Who Play Chess   (ChessManiac.com, 2015-02-02).
 
Chessmasters Who Play Poker:   Zuzana Borosova  (Shark Cage),
Jennifer Shahade,  Alexandra Botez.

Chess Vendors :

Chess Piece Sizing Guideline  by  ChessUSA.
The Chess Store   |   Wholesale Chess   |   Chess Geeks
Chess House   |   House of Staunton
UK :   The Regency Chess Company
India :   ChessBazaar   |   Royal Chess Mall

"Build a Chess Board"   by  Steve Ramsey (2008)   | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
 
"Searching for Bobby Fischer" (1993):  Early life of  Joshua Waitzkin  (1976-).
 
I hate Chess (7:05)  Bobby Fisher  (2020-08-24).
 
Garry Kasparov:  Chess is mental torture (12:01)  KchessK  (2013-10-20).
 
Kasparov's Four Most Memorable Games (12:01)  The New Yorker  (2018-01-19).
 
"Pawn sacrifice" (2014):  Bobby Fisher (1943-2008)  challenges Soviet chess.
 
"The Oxford Companion to Chess"
David Hooper & Kenneth Whyld  (1984, 1993).
 
Max Euwe (1929) and the Thue-Morse sequence in Chess (8:46)
with  Rune Friborg  and  James Grime  (2019-02-08).  See  A010060.
 
History of Computer Chess (12:01)  Sleep Documentary  (ASMR, 2022-01-20).

 
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The Noble Game of Chess


(2018-08-07)   Origins of Chess.  Ancient and modern rules.
The old games of  Chaturanga  and  Shatranj.

Apart from  Go,  all ancien board games can all be classified as single-track  race gamesMancala  is purely strategic  (if you're allowed to count the stones in each pit)  but all the others involve an element of pure luck.  Here are the three most notable examples:

  • The Mesopotamian  Royal Game of Ur.  One of the best designs of all time.  It's  played  with two sets of seven pieces  (at most)  racing on a special board of  20 squares  (two symmetrical 14-square tracks sharing an 8-square middle lane).  The game traditionally uses  4  tetrahedral  dice  with two marked corners.  The outcome of a throw is the total number of marked corners landing at the top;  it's  0,1,2,3,4  (respectively with  1,4,6,4,1  chances  in 16).  The exact rules were found on a late-period  clay tablet from the British Museum  deciphered by  Irving Finkel.  [Play online]
     
  • The Egyptian game of  senet  (the game of passing).  Two sets of  5  pieces,  racing mostly forward on a single 30-square track  (laid out on a 3 by 10 board).  This simple game has been resurrected using the rules reconstructed by the two game historians  Timothy Kendall  and  R.C. Bell (1917-2002).
     
  • Nard  and  Backgammon  (enhanced with the  doubling-cube).

By contrast,  the early forms of chess didn't involve chance at all and made full use of the two dimensions of the game board.

The earliest recognizable form of chess was called  chaturanga  (or  catur  for short).  It appeared in India,  in the seventh century AD and is first mentioned in the  Harshacharita  (biography of Harsha,  c.590-647)  by  Banabhatta.

Shortly thereafter,  the game appeared in Persia under a new name  (shatranj  or  chatang)  and slightly revised rules.  It was possible to win in  shatranj  by capturing all pieces besides the King  (but it was a draw if the opponent could do the same on the next move).

The strongest  shatranj  player on record was  Al-Suli (AD 880-946)  the author of a famous  shatranj  problem known as  Al-suli's Diamond,  which was solved in the 1980s by  Yuri Averbakh (1922-2022).  White wins by capturing the black ferz  which can only move diagonally one square at a time)  without losing his own on the next ply... in 19 moves!

The starting positions in those games were similar to that of chess  (up to a switch of the king and the minister/general/queen).  However,  the pieces had different names, shapes and properties  (somewhat shrouded in uncertainty)  as tabulated below. 

Pawns capture diagonally.  All other pieces capture the same way they move.
ChaturangaShatranjChessAllowed moves :
King  (Raja) King  (Shah) King One square,  laterally or diagonally.
Mantri Vizier / Ferz   One square,  only diagonally.
  Queen Any lateral or diagonal move.
Elephants   Jumps 1 or 2 steps,  diagonally.
  Bishops Diagonally.
Horses Knights Jumps 2 steps,  at 135° of each other.
Chariots   1 or 2 squares,  back,  forth or sideways.
  ChariotsRooks Laterally  (back, forth or sideways).
Padati Soldiers Pawns Forth 1 square  (diagonally to capture).
Elephants, horses and/or knights jump directly from origin to destination.  For other pieces,  a lateral or diagonal move is only allowed if intermediate squares are unoccupied.

At first,  the games were played on an  uncheckered  board of  64  squares  The familiar alternating light and dark colors of modern chessboards first appeared in Europe around 1090.

Some of the boards used were originally intended for an older  race game  called  ashtapada  (eight-legged)  whose exact rules seem lost.  16 special squares called  castles  were marked with crosses  (at the intersections of ranks 1, 4, 5 and 8 with files a, d,e and h).  Such marks are still found on some chessboards of Indian origin,  although their purpose is all but forgotten.

Fantasy

Legend has it that  Chaturanga  was invented for Iadava,  King of Telangana,  who was mourning the loss of his son Adjamir.  The Prince had died heroically to secure victory in a decisive battle at Decsina against the conqueror Varangul.

A young brahmin,  called  Lahur Sessa,  walked 30 days from the village of Manir to the  Andhra  royal palace and presented Iadava with the new game he had designed.  The king was so pleased that he asked the young man to name any reward he wished.  The lad made a simple request related to the 64 squares on the board:  He asked for one grain of wheat on the first square,  two on the second,  four on the third and twice as many grains on every square as on its predecessor.  The King thought that this was a modest price to pay,  until he was advised that the number of grains so named was humongous:

2 64 - 1   =   18446744073709551615
=   3 . 5 . 17 . 257 . 641 . 65537 . 6700417

Incidentally,  that factorization contains the five known  Fermat primes  and a famous factorization of Euler (1732):  232+1 = 641 . 6700417.)

Nice tale, isn't it?  Unfortunately,  that's all it is.  In  some versions,  the young inventor is made vizir for life.  In other versions,  he is executed.

Wheat and chessboard problem

By convention,  the chessboard must be oriented so that the closest corner to the  right  of either player is a  light  square  (light rhymes with right).  This was first specified in print by  Pedro Damiano (1480-1544)  in 1512.   Girolamo Cardano 
 1501-1576  The practice of shading  dark  squares in printed chess diagrams was introduced by  the scientist  Girolamo Cardano (1501-1576).

Three modern moves have no equivalent in ancient chess:

  1. On its first move,  a pawn may travel two squares forward  (if both the destination and the passed-over square are free).
  2. En passant capture  by a pawn is allowed  immediately after  one such move  (it takes place at the passed-over square).  It's customary to stress such a move with the annotation "e.p." (postfixed) which is entirely optional since a diagonal pawn move into an empty square can only occur by virtue of an  en passant  capture.  The option is only open on the very next move, which incidentally doesn't void the classical way to gain a tempo by putting the king in check.  (A tempo is gained anyway because preventing check is at the cost of an immediate capture.  This is illustrated by  #48875  or #62178,  where the tempo so gained allows a rook capture  (winning the game)  whether the opponent accepts the pawn check or prevents it using  en passant.  The rule was primarily invented to prevent the newly-minted two-square pawn moves to allow too many "passed pawns"  (pawns with no opposing pawns on their way to promotion).  Only pawns can capture  en passant  (other pieces controlling the square jumped over by a pawn can't capture it  en passant,  although it would have been perfectly logical to allow that).
  3. Castling  (French  roque;  14th or 15th century, in Europe)
    If all squares between the king and a rook are free,  then a legal move consists in moving the rook next to the king and having the king jump over it,  provided  the following conditions are met:
    • The king and the rook have never moved before.
    • No square in the  path of the king  is under attack.

Two more additions have transformed traditional chess into the game which is most commonly played today,  especially online:

  1. The chess clock.  Originally introduced merely to avoid tournament games that could be so long that they would routinely be  adjourned  from one day to the next,  the clock has become such a dominant part of modern games that people routinely win lots of games merely by outpacing their opponents.  With some silly local rules, a player who doesn't have enough material to mate may be declared the winner.  Arguably,  a perversion of chess.
  2. The Elo rating system.  It has outgrown its original purpose to organize tournaments for all categories of players  (you're banned from lower grades when you become too strong).  Improving one's rating may become the most important goal to achieve. ; At all strength levels from utmost beginner to World champion  (World champion Magnus Carlsen once stated that his top priority was to achieve an Elo of 2900 rather than retain his World title).

In 1972,  the journalist  Tim Krabbé (1943-)  composed,  as a joke,  a  chess problem  whose solution involves a  vertical castling  on the "e" file using a rook created by pawn promotion which had never moved!  Krabbé even put forth the notation  O-O-O-O  for this hitherto unused third type of castling.  Shortly thereafter,  a new wording of the laws of chess was enacted to disallow that.

Chess used to be played until the king was actually captured.  This meant that a player who didn't move out of check  (or even moved into check)  would lose by having the king captured on the next turn,  unless the opponent blundered the game away.

To avoid such endings,  it's now illegal to move into check or not to move out of check.  To better enforce that law,  whoever puts a king in check must  announce  it.  In several languages,  the plural form of such announcements morphed into the name of the game itself  (chess  is a corrupted form of  checks  in English;  the game is called  échecs  in French).

One interesting consequence of that modern rule is the possibility of  stalemate  (French:  pat)  which is a situation when a player is not in check but has no legal move available.  This is now declared a  draw.  In some endgames,  the goal of the dominating player thus becomes to force  checkmate  while avoiding a stalemate situation.

Some obsolete rules considered a  stalemate  a  win  for whoever was called to play from such a situation.  This was the case in England until 1800.

The German term  Zugzwang  (capitalized if German spelling is to be respected)  denotes a configuration which is less favorable if you have to move first than if you don't,  especially in endgame situations very near to a  checkmate  or  stalemate.  (In  combinatorial games theory  the term is sometimes used to denote a losing situation for whoever has to move first.)

The  oldest extant game  of modern chess was played in 1475 in  Valencia  between  Don Franci de Castellvi  (White)  and  Narciso Vinyoles  (Black).  The game illustrates a famous poem entitled  Scachs d'Amor  (Chess Game of Love)  written in Catalan  (more precisely  Valencian)  by  Castellvi  (Venus),  Vinyoles  (Mars)  and  Mossèn Bernat de Fenollar  (Mercury).

Oldest Chess Game Ever Recorded (4:43)  Antonio Radic,  born 1987-06-16  (Agadmator, 2017-09-08)

Caissa  (Scacchia)

Caissa  (pronounced ky-eé-sah)  is a  nymph  of Greek mythology who became known as the  patron godess  of chess after a celebrated  poem  written in 1763 by the young  William Jones (1746-1794)  and entitled  CAISSA or The Game at Chess; a Poem.

The poem of Jones was itself inspired by a  658-line poem  in Latin called  Scacchia Ludus  (The Game of Chess)  due to  Marco Girolamo Vida (c.1485-1566)  who wrote it around 1513,  as Chess in its modern form was gaining popularity in Europe.  It was first published anonymously in 1525 before appearing officially under Vida's name in 1527.

Vida's famous poem also inspired the Polish  narrative poem  "Szachy"  (Chess)  published in 1564-1565 by  Jan Kochanowski (1530-1584).

In many languages,  the name of the game of chess is related to the name of the nymph Cassia  (herself called  Scacchia in Vida's Latin poem).

Chaturanga   |   Shatranj
Checkmate   |   Laws of Chess   |   Chess960 (1996)
 
History of Chess (7:05)  Wesley  (2014-10-09).
Cultural History of Chess (39:50)  Rick Knowlton  (AncientChess.com, 2014-06-30).


(2018-09-11)   Chess Tables,  Boards and Mats.
Various ways the actual chess playing surface is provided.

The generic term of  chessboard  (or just  board)  is used for all of these,  but it need not be an actual rigid board.  It can also be inlaid into a dedicated table or,  for best portability,  a mat can be used which can be rolled up  (or folded, if made out of silicone).

In the US,  the most common  size  for tournaments features  2.25''  squares  (57 mm).  In metric countries,  it's nominally  55 mm.

The playing surface itself is thus  18''  (46 cm).  Typically about  20''  with the borders which often feature two sets of rank numbers and file letters  (to accomodate both players).

Smaller boards are  2''  (51 mm)  or  50 mm.  Larger ones are  60 mm.  (about 2 3/)  rarely  2.5''  (63.5 mm).  Anything outside that range is unsuitable for competition  (especially for quick  bullet games).

Among many others  Wholesale Chess  offers 60 mm  mahogany-and-maple boards for  $80  or  $90  (with notation).  The playing surface on those boards is exactly  19''.  They measure  21½''  with the borders.

I love the look and feel of a  borderless  regulation board  (2¼'' = 57 mm)  which spans only  18½''.  (If borders with notation are ever needed,  such a board can be placed on top of an ordinary tournament mat.)  The best-bang-for-the-buck I found is the inlaid mahogany and maple  Zelus chessboard  ($55)  which comes double-boxed for shipping  (Amazon even puts that double box in an oversized shipping box of their own.)

Such high-quality borderless chessboards can also be used in a customized table or a one-of-a-kind frame  (the playing surface can be mounted recessed, flush or raised, according to taste).  That's a cost-effective way to bypass the time-consuming process of finishing a good playing surface by hand.  If you make your own frame,  consider providing some substantial rounding or overhang on the outside edges to make the assembly easy to pick up  (most commercial products don't).

Arguably,  the board need not match the colors of the pieces.  Playability is hindered when ebonized pieces are  camouflaged  on black squares.

Husaria #6 Chessboard  (57mm = 2¼'')  maple and padauk  ($45).
Polish #5 Chessboard  (50mm = 1.97'')  mahogany and sycamore  ($45).
 
3 types of chess mats (1:54)  by  Wholesale Chess Mats  (2012-08-03).
$450: The Stack Chess Board (5:16)  by  Raphael  (Chess House, 2016-01-19).
A Dozen Chessboards (9:02)  by  Jonas Znidarsic  (2013-02-27).
Ulbrich Spieledesign


(2018-09-07)   Chessmen.
Recommended sizes.

When the game of chess is discussed abstractly,  we talked about pawns and pieces.  The word  chessmen  is normally used only for the physical objects made from wood, metal, stone, clay or plastic.

In modern tournament play,  only minor variants of the  Staunton  chessmen are used.  The official tournament guideline states that the base diameter of the king should be no more than 75% of the side of a squares on the chessboard.  Four pawns should barely fit into a square  (base diameter being 50% the side of a square).

Standard Dimensions of Staunton sets :
Number 234567
King Height 2.5''2.75''3.15''3.54''3.9''4.5''
King Base ''''''''''''
Queen Height ''''2.76''3.23''3.4''''
Queen Base ''''''''''''
Pawn Height ''''1.42''1.69''1.8''''
Pawn Base ''''''''''''
Square 1''1.3''1.5''2''2.25''2.75''
Board 10''13.6''15.75''19''21''24''

 Come back later, we're
 still working on this one...

Some Variants of the Staunton Design :
StyleKingBaseMaterialWeighted2xQ(Best) ColorsPrice
Nero4.25''1.85''Polymer OKOK Dark & Light Brown $75
Hastings4.0''1.8375''Plastic OKOK Red & Natural $25
Staunton3.75''1.75''Plastic OKOK Black & Natural $23
Zagreb3.75''1.5''Rosewood OKOK Dark & Light $120
Marshall3.5''1.45''Silicone NoOK Black & White $17

My own plastic tournament set,  for use with a standard  2¼''  mat,  is the  common  3.75''  Staunton design  highlighted  above.

With the slim  Zagreb '59  design,  a tall king  (3.9'')  can fit nicely on a standard  2¼''  board.  I bought the new weighted boxwood set shown below off of eBay directly from India  (for  $68.64,  including expedited shipping from  Amritsar to Los Angeles).  It arrived in less than  4  days.

 3.9'' Russian Zagreb '59 Series

The above picture shows  2''  squares,  which are a bit too small for the  Zagreb  pieces whose precise measurements are listed below:

Zagreb  '59   Measurements   (3.9 ''  nominal)
  MassHeightBase
King57 g 3.87 ''98.3 mm 1.69 ''42.8 mmK
Queen53 g 3.50 ''88.9 mm 1.59 ''40.5 mmQ
Bishop39 g 3.08 ''78.2 mm 1.42 ''36.0 mmB
 Knight 46 g  2.78 ''  70.5 mm   1.45 ''  37.0 mm  N 
Rook38 g 2.23 ''56.7 mm1.43 ''36.3 mmR
Pawn17 g 1.99 ''50.5 mm1.20 ''30.4 mmP
Matching Square Size 2.25 ''57.2 mmS
This stylish East-European design is a major variant of the Staunton style.  The  Zagreb  design is characterized by counterchanged  finials  and  distinctive  square-fronted Russian knights.  The bishops have  unslotted  tops in the shapes of the  bulbous miters  worn by bishops of the  Eastern Orthodox Church.  They differ from the splitted pointed Western miters of the  Roman Catholic Church,  which inspired the slots of the bishops in the original Staunton pattern.
 
The  Zagreb  design was launched on the occasion of the  1959 Candidates Tournament  held in  Yugoslavia,  in Zagreb  (capital of Croatia)  Belgrade  (Capital of Serbia)  and the touristic town of  Beld.  Eight leading contenders  (including  Bobby Fisher,  then 15 years old)  were competing for the right to challenge  the reigning  World Champion  Mikhail Botvinik (1911-1995)  for the crown he had been holding continuously since 1948,  with a single interruption in 1957-1958.  The legendary Mikhail Tal (1936-1992)  won and went on to fetch the World title the following year,  in Moscow,  but lost the rematch in 1961.  Tal remained popular well after that.  So did the Zagreb pieces.
 
I got this chess set  in spite of  the blocky aspect of its knights,  which turns out to be an acquired taste.  It's now my favorite set to play with.

The ideal square size for a given set of pieces depends only on the  bases,  not the heights.  Two good rules of thumb are floating around.  The first one is simple but the second one is more robust and more general  (it applies to all round designs,  even outside the Staunton family):

  • The king base should be about  75%  of the side of the field square.
  • If a king and a queen are diagonally adjacent,  the distance between them should be greater than the bishop's base.
The latter rule allows play by sliding the pieces even in the worst possible case  (when a bishop moves between the two largest pieces which can legally be adjacent to each other).  If that's your preferred style,  this should be the primary consideration and the ensuing inequality must be satisfied with some room to spare  (to allow for misalignments during actual play).  Usually,  even people who like sliding the pieces will lift them when the squeeze seems tight.
 
Two unreliable criteria are used by some salespeople:  The square should be twice the base of the pawn  (i.e.  4 pawns can fit in a square)  or half the height of the king  (i.e.,  a fallen king spans two squares).

The first rule corresponds to the rough formula  K = 0.75 S.   The second one says that the  diagonal  of the square must be greater than the bishop's base plus half the sum of the king and queen bases.  Namely:

S Ö2     >     B  +  (K+Q) / 2

For the  above dimensions  of the Zagreb pieces,  those two formulas give:

S  =  2.25 ''  or  57.2 mm           S  >  2.16 ''  or  54.9 mm

This does indicate that a regulation chessboard  (55 or 57 mm)  is nearly ideal for the above zagreb pieces  (while a 2'' board is definitely too tight).

Let's do the same computation for the tournament plastic set I use:

Classical Staunton Measurements   (3.75 ''  nominal)
  MassHeightBase
King68 g 3.70 ''93.9 mm 1.79 ''45.4 mmK
Queen62 g 3.12 ''79.2 mm 1.71 ''43.5 mmQ
Bishop37 g 2.78 ''70.6 mm 1.43 ''36.3 mmB
 Knight 41 g  2.40 ''  61.0 mm   1.38 ''  35.1 mm  N 
Rook46 g 2.21 ''56.1 mm1.50 ''38.1 mmR
Pawn22 g 2.07 ''52.6 mm1.26 ''32.0 mmP
American Regulation Square 2.25 ''57.2 mmS

The aforementioned guideline formulas would give:

S  =  2.39 ''  or  60.6 mm           S  >  2.25 ''  or  57.2 mm

Thus,  those pieces can be played on regulation US mats  (57.2 mm).  An oversized  60 mm  board would be fine too.

Our next example involves the French style which was dominant throughout Europe before the Staunton pattern displaced it for serious play.  It's best called  Régence.  Drop the accent if you must,  but avoid the  Regency  misnomer,  since this chess style was actually named after what was the undisputed nevralgic center of Chess in the eighteenth century:  Le café de la Régence  in Paris,  France  (best left untranslated).

Incidentally,  Howard Staunton  (1810-1874)  crowned himself  World champion  in  1843,  when he won his return match against the most prominent  Régence  player of the time,  Pierre Saint-Amant  (1800-1872).

Régence Chessmen Measurements   (4.3 ''  nominal)
  MassHeightBase
King72 g 4.36 ''110.8 mm  1.54 ''39.1 mmK
Queen69 g 4.11 ''104.4 mm  1.50 ''38.1 mmQ
Bishop43 g 2.97 ''75.4 mm 1.31 ''33.2 mmB
 Knight 51 g  3.80 ''  96.6 mm   1.31 ''  33.2 mm  N 
Rook42 g 2.58 ''65.5 mm1.31 ''33.2 mmR
Pawn29 g 2.15 ''54.6 mm1.26 ''32.0 mmP
European Regulation Square 2.17 ''55.0 mmS

For those slender pieces,  the above guidelines would give:

S  =  2.05 ''  or  52.1 mm           S  >  2.00 ''  or  50.1 mm

So,  a  2''  board is slightly too tight,  albeit aesthetically stunning.

Staunton chess set   |   Luxury chess sets  (2018)   |   Arabian Knight Series  ($256)
 
Staunton designs (13:00)  by  Rick Knowlton  (AncientChess.com, 2011-03-15).
 
The Lewis Chessmen (15:00, 14:12British Museum  (2013-11-11).
The Chamber of Lewis Chessmen (8:27)  by  Irving Finkel  (The British Museum, 2017-09-24).
The Isle of Lewis Chessmen (9:56)  by  Rick Knowlton  (AncientChess.com, 2011-04-14).
 
Early Régence Chess Set (4:37)  by  Alan Dewey  (chessspy.com, 2012-08-31).
Chess Sets of the 19th Century (9:02)  by  Alan Dewey  (chessspy.com, 2015-01-03).
One of five extant 1849  (first year)  Jaques of London Stauton chess sets (5:57)  by  Alan Dewey  (chessspy.com, 2013-03-03).
 
20th Century Designs: Josef Hartwig, Man Ray, Max Ernst (5:30)  AncientChess  (2016-03-31).
2010 Shera Series (2:45)  by  Chess Bazaar  (2014-11-19).
Gorgeous Re-Finished Arabian Knight Luxury Chess Set (10:32)  by  Richard Walters  (2017-06-04).
 
10  Ugly Chess Sets for the Rich (2:31)  allTop Ten  (2014-08-29).
 
Rebuilding the 700 AD chessmen from Afrasiab (4:43)  Rick Knowlton  (AncientChess, 2014-08-10).
 
Carving chess pieces in India (12:57)  Mandeep Singh Saggu  (Mandeep Handicrafts, 2016-08-15).


(2018-11-09)   Wood and Other Material Used in Chess
Ivory,  bone,  wood,  plastic  and  polymer.

For chess pieces:

For chessboards,  chess boxes and furniture:

Rare Woods USA  in Mexico, Maine  (video).
2" x 2" Exotic Wood Blanks  (for turning)  BellForest.
Lumber  Home Depot.

Ebonizing :

Traditionally,  Boxwood  was used for white pieces and  ebony  for black pieces.  Both kinds of wood are denser than water with very fine grain which makes them exceptionally well suited for turning and fine carving.

Because of recent restrictions on the harvest of ebony,  boxwood is increasingly used for black pieces as well using what's call  ebonization,  which can be done several different ways.

Black color is obtained when  ferric acetate  reacts with wood tannin.  This reaction uses the same basic principle as  iron-gall ink  (upon which Western civilization was arguably founded).

To make a good  ebonizing solution  at home,  first clean some steel wool thoroughly with soap and water  (to remove any trace of oil which would hinder the rest of the process).  Rinse it well.  Let it soak for several days at room temperature in a mixture of cleaning vinegar  (6% or 8% acetic acid)  and hydrogen peroxide  (heating can speed up the process,  if needed).  Ferric acetate  will form:

2 Fe  +  3 H2O2   ®   2 Fe(OH)3
Fe(OH)3  +  3 CH3COOH   ®   Fe(CH3COO)3  +  3 H2O

This is a  mordant  which blackens wood by reacting with the  tannin  in it.

 Come back later, we're
 still working on this one...

Ebonizing wood with iron acetate
Formation of Iron Acetate in Solution (2:15)  by  Chad, the C  (2017-09-01).
Three Ways to Ebonize Wood (39:30)  by  Les Casteel  (2013-10-30).

 USCF Chess Bag
(2018-10-31)   Chess Bag

The bag I recommend to carry full-sized pieces, a rolled-up mat, a clock, scoresheets and pens is from the USCF  ($25).


(2018-08-07)   Chess Clock
Some controversial aspects of timed games.

Time limitations on chess games are of relatively recent origins.  Chess clocks have been used in competition since the London International Tournament of April 1883.  In official FIDE tournaments, the chess clock always sits to the rignt of whoever plays with the  black  pieces.

Time controls were born out of necessity to make the organization of tournaments possible.  The possibility of  losing on time  was originally just a way to enforce those time limits without altering the nature of the game.

Bonus and Delay :

Those are the two simplest ways to force fast play on low time without making it humanly impossible to execute decent moves.  In practice,  these two methods are  never  used together  (although they're not incompatible).

  • Bronstein delay  is also called  simple delay  or  US delay.  The player's alloted time doesn't start to be debited until a certain preset  delay  has ellapsed.  A player who plays  every  move faster than this preset delay will never run out of time.
  • Fischer increment  is a preset  bonus  time  which is added at the beginning of every turn.  The unused portion of those bonuses can accumulate so that a future move which requires more consideration can be played less recklessly.

Currently,  almost all  classical chess  tournaments endorsed by the  Worldwide Chess Federation  are played in 90 minutes  (per player)  for the first 40 moves and 20 minutes for each side for the rest of the game,  with a 30-second  Fischer increment  per move  (starting with the very first move).  That gives each player 110 minutes to complete the first 40 moves.  (That's code 04 on the  Wholesale Chess Advanced Digital Game Timer.)

For the World Championship  (and the qualifying Candidate Tournament)  the time limits are 100 minutes for the first 40 moves, 50 minutes for the next 20 moves and 15 minutes for the rest of the game.  Again with a 30-second Fischer increment starting at the first move.  (That's code 05 on the  Wholesale Chess Advanced Digital Game Timer.)

Japanese Byo-Yomi:

This is a more complicated time-control used for mostly for  shogi  and  go  but digital chess clocks often allow it.

 Come back later, we're
 still working on this one...

Gentleman's Rules:

It's a monstrosity to grant a win in chess to a player who doesn't even have enough pieces to mate  (although it's sometimes done in automated online play).  In that case,  a player is awarded a draw if the other runs out of time.

  • The game is an instant draw if neither player has enough to mate.
  • Furthermore,  a good  Gentleman's Agreement  in a timed game is to resign with a bare king if the other side has at least:
    • A queen.
    • A rook.
    • Two bishops.
    • A bishop and a knight.

It would be nice if chess-playing software enforced this automatically.

In over-the-board play,  someone who grabs a piece which has at least one legal move must play that piece  (the old-school  touch-move rule).  A legal move is final when the player lets go of the piece.  I argue that no penalty should be incurred when an illegal move is corrected before the clock is punched  (but punching the clock after an illegal move forfeits the game).

Time control   |   Chess Clock   |   Draw by agreement
ACP demands standardizing time controls in chess  (ChessBase, 2007-09-16).
Time Controls  (Chess.com, 2008-01-21).
Time Controls in the US  by  Greg Shahade  (USCF, 2012-09-21).
Tournament Life in the US   (Continental Chess Association).
Time control notation explained?  by  Derek Chiang  (Chess StackExchange, 2015-01-04).
How exactly do time controls work?  by  BradB132  (Reddit, 2015).
 
Carlsen loses because his opponent made an illegal move!  (7:12)   Antonio Radic  (Agadmator, 2017-12-29).
 
Advanced Digital Game Timer (17:08)  by  Wholesale Chess  (2017-07-07).
 
Over-the-board (OTB) Chess Tournaments (30:09)  by  Levy Cozman  (GothamChess, 2022-06-13).


(2022-02-07)   Naming the 64 squares of the Chessboard
By far, the most common way is the  algebraic  one.  Others still exist.

 Come back later, we're
 still working on this one...


(2018-08-13)   Standard algebraic Notation   (Philipp Stamma,  1737)
Only one notation survives to record chess games,  with minor variants.

Each square is identified by a lowercase letter from "a" to "h" according to its file and a numeral from "1" to "8" according to its rank.  Squares are either  light  or  dark.  The corner squares to the right of either player  (h1 and a8)  are light.  In the starting position,  the white queen is on  d1  (a light square)  and the black queen is on  d8  (a dark square).  You may want to remember that queens start on their own colors.

Each type of piece  (besides the pawns)  is identified by a single capital letter:  K, Q, B, N, R  (at each move,  White  moves first and  Black  second).  When a piece is not specified,  a pawn move is understood  (the abbreviation  P  is deprecated).

In case of ambiguity  (when the landing square is accessible to two like pieces)  give the lowercase letter identifying the  file  (column)  where the piece is moving from  after  the name of the piece.  If that doesn't lift the ambiguity,  give the number of the  rank  instead.

Conceivably,  you might need to name the starting square fully,  by file and rank,  in the extremely rare case where the destination square is accessible to  three  like pieces at the corners of a rectangle.  Prerequisites for such a situation include a promotion to knight,  two queenings or two promotions to bishops!  Yet,  if you're a programmer,  you must anticipate such a weird thing.

  • Long  and short  castling  are respectively denoted  O-O-O  and  O-O.
  • When a pawn is promoted,  the piece it becomes is indicated after an equal sign  (formerly, a slash was used).  For example:   67.  c8=Q
  • No special notation is used  (or needed)  for  en passant  capture.
  • A move which puts the king in check is followed by a  plus sign  (+).
  • Checkmate is indicated by a  pound sign  #  (++ is deprecated).

In the computer era,  it's important to always record moves in the tersest way  (so plain text searches can fetch them).  However,  in handwritten or printed scores,  it's nice to name the captured piece for the sake of readability.  For example,  the key move in  Legal's mate  could be  written :

5.  Nxe5   BxQd1

Likewise,  one of six abbreviated  annotations  of one or two characters,  can be given after any move,  except  a checkmate or a forced move.

  • Brilliant  (!!).
  • Excellent  (!).
  • Debatable  (!?).
  • Dubious or inaccurate  (?!).
  • Mistake  (?).
  • Blunder  (??).

This is in addition to the automatically affixed qualifiers not subject to any judgement call:

  • Check  (+).  Marks a move that would allow capture of the king on the next turn.
  • Double-check  (++).  In check by two different pieces, the king has to move.
  • Forced  (,).  Only legal move.  (Optional but helpful symbol, replacing the  tombstone.)
  • Checkmate  (#).  The king is in check and can't get out of it.  Game over.
  • Single-line  (,,).  Obvious or sample choice  (the other possibilities needn't be discussed).  This may also mark an irrelevant  waiting move  or one of several moves which vacate the same square in a discovery attack.  A double-comma indicates two or more options.  More than two commas must indicate the exact number of those options.

The above use of single or multiple commas as symbolic comments after a move was my own proposal.  (2022-02-20).  Some authors have used a typographical tombstone  for both purposes,  often without making a clear distinction between forced moves and single line.  The commas are, of course, available directly from the keyboard are are thus painless to use.  They are unobtrusive enough so that they can sometimes serves a similar purpose but some authors employ that to indicate what they think is the only  reasonable  move.
 
Commas are unobtrusive enough to be ignored by the uninitiated.  Yet, a commonly available punctuation mark for forced moves was logically needed  (it's a routine comment for which none of the other comment symbols apply.  Note that other punctuation marks which were not available for the purpose include the semicolon  (;)  which is already codified to indicate in computer notation that the rest of a line is comment directed at human readers.

Unfortunatey,  the names of the pieces and their abbreviations are different in different languages  (in addition,  following  Maurice Beaucaire,  the French used to replace "c" and "e" by "ç" and "é" for in square coordinates, to help distinguish the two).  For international communication,  graphical hieroglyphs for the pieces are often used in print,  although I find them harder to read  (if your eyes are on the wrong side of the half-century mark).

English K  Q  R  B  N  (P) 
FrenchRDTFC(P)
German, Dutch, SwedishKDTLS(B)
  Italian, Spanish  RDTAC(P)
PortugueseRDTBC(P)
CzechKDVSJ( )

Reversible (long) notation :

Formerly,  both  the origin and destination were always recorded.  This convention is now fairly rare.  It's known as  long  or  reversible  because it makes it easy to move back from a position given in a diagram  (especially since the names of captured pieces are always given with the destination square).  For example:

1. e2-e4   e7-e5

Chess notation   |   Standard algebraic notation (SAN)   |   Descriptive notation (deprecated since 1981)
Foreign Names of Chess Pieces (ChessOps)
National Descriptive Notations  by  John Savard  (Quadibloc).
 
Forsyth-Edwards Notation (FEN)   |   David Forsyth (1854-1909)
 
Portable Game Notation (PGN, 1993)   |   Numeric Annotation Glyphs (NAG, 1994)   |   Steven J. Edwards (1957-2016)
 
ICCF numeric notation (1803)   |   J. W. D. Wildt ()   |   Johann Koch ()
 
Uedemann's Code ()   |   Louis Uedemann (1854-1912)
 
Gringmuth's system (1866)   |   D.A. Gringmuth ()


(2018-08-13)   The most common chess openings:
An advanced player's  repertoire  consists in familiarity with many lines.

White  has 20 possible first moves  (2 per pawn and 2 for each knight)  corresponding to the  20  headings below,  listed in order of popularity.  Because the  Sicilian Defense  (1. 1. e4 c4)  is so strong,  the second-most-popular opening move for White  (1. d4)  can be considered stronger than the most popular one  (1. e4)  whose continuations take up more space in this list than all the other variations combined.

This structured list introduces the  names  of some notorious openings discussed among players.  The  Oxford Companion to Chess  goes well beyond this,  with  1327  named opening lines.

1. King's Pawn Opening   1. e4
  • Sicilian Defense :   1. e4 c5
  • 1. e4 c5 2. c3   Alapin Variation (an "anti-Sicilian" avoiding  open Sicilian).
    1. e4 c5 2. c3 e6
    1. e4 c5 2. c3 Nf6 3. e5 Nd5
    1. e4 c5 2. c3 Nf6 3. e5 Nd5 4. c4 e6?? 5. cxd5! Qg5? (1100 Robot).    Cartoon
    1. e4 c5 2. c3 d5 3. exd5 Qxd5   Barmen Defense.
    1. e4 c5 2. c3 d6 3. d4 Nf6 4. Bd3 Nc6   Gambit declined.
    1. e4 c5 2. c3 d6 3. d4 Nf6 4. dxc5 Nc6 5. cxd6 Nxe4   Gambit accepted.
    1. e4 c5 2. c3 e5 3. Nf3 Nc6 4. Bc4
  • 1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3   Open Sicilian :
          5... g6   Sicilian Dragon.
          5... e6   Scheveningen.
          5... Nc6 6. Bg5 e6   Richter-Rauzer.
          5... Nc6 6. Bc4 e6   Fischer-Sozin.
          5... Nc6 6. Be2 e5   Boleslavsky.
          5... a6 6. Bg5 e6 7. f4   Najdorf.
          5... a6 6. Bg5 e6 7. f4 Qb6 8 Qd2 Qxb2   Poisoned Pawn.
          5... a6 6. Bg5 e6 7. f4 b5 8. e5 dxe5 9. fxe5 Qc7!   Polugaevsky, 1977.
    1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4   Hyperaccelerated Dragon, Fianchetto.
    1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 g6   Accelerated Dragon.
    1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 g6 5. c4   Maróczy_Bind.
    1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 e5 6. Ndb5!   Sveshnikov.
  • 1. e4 c5 2. Nf3 Nc6 3. Bb5   Rossolimo Variation :
    1. e4 c5 2. Nf3 Nc6 3. Bb5 Nf6 4. Nc3  
    1. e4 c5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6  
    1. e4 c5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4?? b5 5. Bb3 c4   Noah's Ark Trap.
  • 1. e4 c5 2. d4 cxd4 3. c3   Smith-Morra Gambit :
    1. e4 c5 2. d4 cxd4 3. c3 dxc3 4. Nxc3 Nc6 5. Nf3 e6
        6. Bc4 Qc7!? 7. Qe2 Nf6 8. O-O-O? Ng4! 9. h3??   Siberian Trap.
  • 1. e4 c5 2. b4   Wing Gambit.
    1. e4 c5 2. b4 cxb4 3. a3 bxa3
    1. e4 c5 2. b4 cxb4 3. a3 d4 4. exd4 Qxd4 5. Bb2
    1. e4 c5 2. b4 cxb4 3. a3 d4 4. exd4 Qxd4 5. Nf3
    1. e4 c5 2. b4 cxb4 3. a3 d4 4. exd4 Qxd4 5. bxa3 Qe5+ Qxa1    Cartoon
  • 1. e4 c5 2. a3!?   Modern Anti-Sicilian  (IM Sergei Soloviov, 1957-).
  • 1. e4 c5 2. f4?   Grand Prix Attack   (McDonnell, 1834).
    1. e4 c5 2. f4 e6   McDonnell.
    1. e4 c5 2. f4 d5 3. exd5 Nf6!   Tal Gambit  (1979).
    1. e4 c5 2. f4 d5 3. Nf3   Tal Gambit Declined  ("Toilet Variation").
  • 1. e4 c5 2. Bc4? e6!   Bowdler attack.
  • Caro-Kann Defense :   1. e4 c6
    1. e4 c6 2. d4 d5
  • 1. e4 c6 2. d4 d5 3. e5 Bf5   Advanced Variation
    1. e4 c6 2. d4 d5 3. e5 Bf5 4. h4   Tal Attack
    1. e4 c6 2. d4 d5 3. e5 Bf5 4. g4   Bayonet Attack.
    1. e4 c6 2. d4 d5 3. e5 Bf5 4. Nc3 e6 5. g4!   Shirov Attack.
  • 1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Bf5 5. Ng3 Bg6   Classical main line.
    1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nd7   Modern variation.
    1. e4 c6 2. d4 d5 3. Nd2 dxe4 4. Nxe4 Ne7 5. Qe2!? Nf6?? 6. Nd6#    Cartoon
    1. e4 c6 2. d4 d5 3. Nd2 dxe4 4. Nxe4 Bf5   Capablanca Variation.
        5. Ng3 Bg6 6. h4 h6 7. Nf3 Nd7 8.h5 Bh7   Spassky Variation.
  • 1. e4 c6 2. Bc4?!   Hillbilly Attack.  Cartoon
  • Open Game :   1. e4 e5   (Double King's Pawn Opening)
    1. e4 e5 2. Nf3   King Knight's Opening.
    1. e4 e5 2. Nf3 Nf6   Petrov Defense  (Russian Game).
    1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nxf7   Cochrane Gambit.
    1. e4 e5 2. Nf3 Nf6 3. Nxe5 Nc6 4. Nxc6 dxc6   Stafford Gambit  (1950).
    1. e4 e5 2. Nf3 Nf6 3. d4 Nxe4   Steinitz attack.
    1. e4 e5 2. Nf3 d6   Philidor Defense.
    1. e4 e5 2. Nf3 d6 3. Bc4 Bg4 4. Nc3 g6 5. Nxe5 Bxd1 6. Bxf7+ Ke7 7. Nd5#   Legall's mate.

    1. e4 e5 2. Nf3 d5!? 3. exd5 Bd6   Elephant Gambit.
    1. e4 e5 2. Nf3 f5?!   Latvian GambitGreco Countergambit.
    1. e4 e5 2. Nf3 f6?   Damiano Defense  (1512).
    1. e4 e5 2. Nf3 f6? 3. Nxe5!   Damiano Gambit.
  • 1. e4 e5 2. Nf3 Nc6   Damiano's tipSpanish, Italian, Scotch,  etc.
  • Ruy López  (Spanish game):
    1. e4 e5 2. Nf3 Nc6 3. Bb5
    1. e4 e5 2. Nf3 Nc6 3. Bb5 a6   Morphy defense.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7   Closed defense
        6. d3   Modern line   [Video by Peter Svidler]
        6. Re1 b5 7. Bb3 d6 8. c3 O-O   Main lines...
        6. Re1 b5 7. Bb3 d6 8. c3 O-O 9. h3  
        6. Re1 b5 7. Bb3 O-O 8. c3 d5   Marshall Attack   [video]
    1. e4 e5 2. Nf3 Nc6 3. Bb5 f5   Schliemann defense  (Jaenisch gambit, C63).
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Nge7   Cozio defense.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3  Classical defense  (Oskar Cordel).
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3 Nf6   Benelux.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3 f5   Cordel gambit.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3 Bb6   Charousek.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3 Qe7   Boden.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. O-O   Zaitsev.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. Bxc6? dxc6 5. Nxe5 Qd4
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6   Berlin Defense.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Nxe4   Rio Gambit Accepted.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Nxe4 5. d4 Nd6 6. Bxc6!?
        6. ... bxc6 7. dxe5 Nb7 8. Nc3 Be7 9. Bf4 O-O 10. Re1   Lasker.
        6. ... dxc6 7. dxe5 Nf5
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Ng4!?
        5. h3? h5! 6. hxg4?? hxg4   Fishing Pole  trap.
    1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. d3   Anti-Berlin Defense.
  • Italian game  (Greco, 1620):
    1. e4 e5 2. Nf3 Nc6 3. Bc4
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nd4?! 4. Nxe5?   Blackburne Shilling Gambit    Cartoon
    1. e4 e5 2. Nf3 Nc6 3. Bc4 d6   Paris Defense.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6   Two-Knights Defense.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5   Fried-Liver Attack.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Na5!   Polerio Defense.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Nxd5!? 6. d4   Lolli.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Nxd5!? 6. Nxf7!
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 Bc5!? 5. Nxf7? Bf2+   Traxler.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 Bc5!? 5. Bxf7+ Ke7   Wilkes-Barre.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Be7   Hungarian Defense.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3   Giuoco Piano.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. Ng5   [ Fried-Liver Delayed ]
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. d3   Giuoco Pianissimo.
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. b4   Evans Gambit.  [ Young Morphy ]
    1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. Bf7+ Kxf7 5. Nxe5+ Nxe5  Jerome Gambit.
  • Scotch Game  (del Rio, 1750.  Edinburgh-London, 1824):
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bb5   Relfsson Gambit  ("MacLopez").
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4   Scotch Gambit.
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Bc4 Bb4+   London Defense.
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. c3   Göring Gambit (1857).
  • 1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Bc5   Classical Scotch Game.
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Nf6   Schmidt Variation.
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Qh4!?   Steinitz Variation.
    1. e4 e5 2. Nf3 Nc6 3. d4 exd4 4. Nxd4 Qf6!?
  • 1. e4 e5 2. Nf3 Nc6 3. d4 Nxd4 4. Nxd4   Lolli Variation.
    1. e4 e5 2. Nf3 Nc6 3. d4 Nxd4 4. Nxd4 exd4 5. Qxd4
    1. e4 e5 2. Nf3 Nc6 3. d4 Nxd4 4. Nxd4 exd4 5. Bc4!?   Napoléon gambit.
  • Ponziani Opening:   (Lucena, 1497)[ video ]
    1. e4 e5 2. Nf3 Nc6 3. c3   Superseded by the Spanish and Italian games.
    1. e4 e5 2. Nf3 Nc6 3. c3 Nf6!   Jaenisch Variation
    1. e4 e5 2. Nf3 Nc6 3. c3 d5
    1. e4 e5 2. Nf3 Nc6 3. c3 f5!?   Ponziani's countergambit  (1769).
  • Dresden Opening :
    1. e4 e5 2. Nf3 Nc6 3. c4
  • Three-Knights Game :
    1. e4 e5 2. Nf3 Nc6 3. Nc3   [ traps ]
    1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6   Four Knights Defense.
    1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. d4   Scotch Variation.  C47
    1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. d4 Bb4 5. Nxe5   Krause Gambit.
    1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. d4 exd4 5. Nxd4   Scotch main line.
    1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. d4 exd4 5. Nd5!?   Belgrade Gambit.
    1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5 Nxe5 5. d4   Halloween Gambit.
  • Vienna Game :   1. e4 e5 2. Nc3
  • 1. e4 e5 2. Nc3 Nf6   Falkbeer Defense.
    1. e4 e5 2. Nc3 Nf6 3. Bc4 Nc6   Main line (C28).
    1. e4 e5 2. Nc3 Nf6 3. Bc4 Nxe4   Frankenstein-Dracula  (Harding, 1976).
    1. e4 e5 2. Nc3 Nf6 3. f4 d5!   Vienna Gambit (C29).
    1. e4 e5 2. Nc3 Nf6 3. f4 d5 4. d3   Steinitz Variation.
    1. e4 e5 2. Nc3 Nf6 3. f4 d5 4. fxe5 Nxe4 5. Qf3   .
    1. e4 e5 2. Nc3 Nf6 3. f4 exf4 4. e5 Ng8 5. Nf3 d4 6. Bf4
  • Max Lange Defense :   1. e4 e5 2. Nc3 Nc6
    1. e4 e5 2. Nc3 Nc6 3. f4   Vienna Gambit.
    1. e4 e5 2. Nc3 Nc6 3. f4 exf4   Vienna Gambit Accepted.
        4. Nf3 g5 5. Bc4 g4 6 .O-O gxf3 7. Qxf3   Hamppe-Muzio Gambit.
        4. d4 Qh4+ 5. Ke2   Steinitz Gambit.
    1. e4 e5 2. Nc3 Nc6 3. Bc4 Nf6 [cf. 1. e4 e5 2. Nc3 Nf6 3. Bc4 Nc6 ]
    1. e4 e5 2. Nc3 Nc6 3. g3   Paulsen variation.
  • Portuguese Opening :  1. e4 e5 2. Bb5  (City of Sneek, 1853).  Butler's Folly.
  • Center Game :
    1. e4 e5 2. d4 exd4 3. Qd4 Nc6
    Danish Gambit  {Severin From, 1867} :
    1. e4 e5 2. d4 exd4 3. c3
  • Bishop's Opening:
    1. e4 e5 2. Bc4
    1. e4 e5 2. Bc4 Nf6 3. Nc3 Nxe4   Blanel Gambit  (Frankenstein-Dracula).
    1. e4 e5 2. Bc4 Nf6 3. d4 exd4 4. Nf3   Urosov gambit (49:45).
    1. e4 e5 2. Bc4 f5?!   Calabrese Countergambit.
  • Scholar's Attack :
    1. e4 e5 2. Qh5   Wayward Queen Attack.
    1. e4 e5 2. Qh5 Nc6 3. Bc4 g6 4. Qf3 Nf6 5... Nd4!
    1. e4 e5 2. Qf3?!   Napoléon Opening.
  • Alapin's Opening:
    1. e4 e5 2. Ne2!?
  • French Defense :   1. e4 e6
    1. e4 e6 2. d4 d5 3. e5 c5 4. c3 Nc6 5. Nf3   Advance Variation.
    1. e4 e6 2. d4 d5 3. Nc3 Nf6   Classical Variation.
    1. e4 e6 2. d4 d5 3. Nc3 Nf6 4. e5 Nfd7   Steinitz Variation.
    1. e4 e6 2. d4 d5 3. Nc3 Nf6 4. e5 Nfd7 5. Nce2   Shirov-Anand Variation.
    1. e4 e6 2. d4 d5 3. Nc3 Nf6 4. e5 Ne4!? 5. Nxe4 dxe4 6. Bc4!  
    1. e4 e6 2. d4 d5 3. Nc3 Bb4 4. e5 c5 5. a3 Bxc3+ 6. bxc3   Winawer
    1. e4 e6 2. d4 d5 3. Nc3 Bb4 4. Bg5 Bb4   McCutcheon
    1. e4 e6 2. d4 d5 3. Nc3 (or Nd2) dxe4 4. Nxe4 Bd7   Fort Knox.
    1. e4 e6 2. d4 d5 3. Nd2 Nc6   Carlos Enrique Guimard (1913-1988).
  • 1. e4 e6 2. Nf3 d5 3. Nc3   Two-Knights variation.
  • 1. e4 e6 2. Nf3 d5 3. e5 c5 4. b4   Wing Gambit.
    1. e4 e6 2. Nf3 d5 3. e5 c5 4. b4 cxb4 5. a3! bxa3 6. d4 Nc6 7. c3
  • Nimzowitsch Defense :   1. e4 Nc6
    1. e4 Nc6 2. d4 d5 3. e5 Bf5
    1. e4 Nc6 2. d4 d5 3. e5 f6
    1. e4 Nc6 2. d4 d5 3. exd5 Qxd5
    1. e4 Nc6 2. d4 e5 3. Nc3 dxe4
    1. e4 Nc6 2. Nf3 e5
    1. e4 Nc6 2. Nf3 f5 3. exf5   Colorado Gambit.
    1. e4 Nc6 2. Nf3 d6   Williams Variation.
  • Scandinavian Defense :   1. e4 d5
    1. e4 d5 2. exd5 Qxd5
    1. e4 d5 2. exd5 Nf6
    1. e4 d5 2. exd5 c6? 3. dxc6   Blackburne-Kloosterboer Gambit
    1. e4 d5 2. Nf3 dxe4 3. Ng5   Tennison Gambit.
    1. e4 d5 2. Nf3 dxe4 3. Ng5 Nf6 4. d3 exd3? 5. Bxe3 h6?
        6. Nf7! Kxf7 7. Bg6+ Kxg6 8. Qxd8   Queen for Knight and Bishop.
  • Pirc Defense (pronounced peerts).  Yugoslav defense.
    1. e4 d6
    1. e4 d6 2.d4 Nf6 3.Nc3 g6 4.f4 Bg7 5.Nf3   Austrian Attack
  • Owen's Defense  (Greek Defense).
    1. e4 b6
  • St. George Defense  (Baker's Defense, Basman Counterattack).
    1. e4 a6 2.d4 b5 3. Nf3 Bb7 4. Bd3 e6 5. O-O Nf6
    1. e4 a6 2.d4 b5 3. c4 e6!? 4. cxb5 axb5 5. Bxb5 Bb7   Three Pawns Attack.
  • King's Gambit:
    1. e4 e5 2. f4
    1. e4 e5 2. f4 exf4   King's gambit accepted  (KGA).
    1. e4 e5 2. f4 exf4 3. Bc4   Bishop's Gambit.
    1. e4 e5 2. f4 exf4 3. Bc4 f5   Lopez-Gianutio Countergambit (C33).
    1. e4 e5 2. f4 exf4 3. Bc4 Qh4+ 4. Kf1   Immortal Opening.
    1. e4 e5 2. f4 exf4 3. Nf3 g5 4. Bc4 g4 5. Ne5 Qh4+ 6. Kf1   Salvio Gambit.
    1. e4 e5 2. f4 exf4 3. Nf3 g5 4. Bc4 g4 5. O-O gxf3 6. Qxf3   Muzio Gambit.
    1. e4 e5 2. f4 exf4 3. Nf3 g5 4. Bc4 g4 5. Bxf7+?!   Lolli Gambit.
    1. e4 e5 2. f4 exf4 3. Nf3 f5   Gianutio Countergambit (C34).
    1. e4 e5 2. f4 Bc5   King's gambit declined; classical defense.
    1. e4 e5 2. f4 Bc5 3. fxe5?? Qh4+   (Novice trap.)
    1. e4 e5 2. f4 d5   KGD;  Falkbeer Countergambit
    1. e4 e5 2. f4 f5?!   KGD;  Panteldakis Countergambit (Greco, 1625)
    1. e4 e5 2. f4 Qf6   KGD: Norwalde variation.
    1. e4 e5 2. f4 Qf6 3. Nf3 Qxf4 4. Nc3 Bb4 5. Bc4  Buecker gambit.
    1. e4 e5 2. Ke2?   Bongcloud.    Cartoon
  • Alekhine's Defense.
    1. e4 Nf6
    1. e4 Nf6 3. d3
    1. e4 Nf6 3. Nc3
    1. e4 Nf6 2. e5! Nd5 3. d4 b5!? 4. Bxb5 c5 5. dxc5? Qa5+ 6. Kf1 Qxb5+   Alekhine's Gambit.
    1. e4 Nf6 2. e5! Nd5 3. d4 Nb6 4. Nf3?! dxe5 5. Nxe5 c6!
    1. e4 Nf6 2. e5! Nd5 3. d4 Nb6 4. d5 Nd5   Lasker Attack.
  • Modern Defense  (Robatsch).
    1. e4 g6 2. d4
    1. e4 g6 2. d4 Bg7 3. Nc3 c6 4. Bc4 d6 5. Qf3   Monkey's Bum Deferred.
    1. e4 g6 2. Bc4 Bg7 3. Qf3 e6 4. d4 Bxd4 5. Ne2 Bg7 6. Nbc3   Monkey's Bum.
  • Adams Defense   1. e4 Nh6   Wild Bull, Hippopotamus.
  • Barnes Defense   1. e4 f6   (1858)Thomas Wilson Barnes (1825-1874). 
  • Polish Gambit   (least played).
    1. e4 b5 2. Bxb5
    1. e4 b5 2. Bxb5 Bb7 3. Nc3 f5!? 4. exf5? Bxg2   Grindewald Attack.
2. Queen's Pawn Opening   1. d4   (A40) 3. Zukertort Opening   1. Nf3 4. English Opening   1. c4   1843   Howard Staunton (1810-1874).
  • 1. c4 e5   Reverse Sicilian
  • 1. c4 e5 2. e3 Nc5 3. Bg2 Bc5 4. Nc3 d6
  • 1. c4 e6   Agincourt Defense
  • 1. c4 c5   Symmetrical Defense
    1. c4 c5 2. Nf3 Nc6 3. Nc3   Two-Knight Variation.  (Tal-Anand,  Feb. 1989).
5. King's Fianchetto Opening   1. g3  (Benko's Opening)
  • 1. g3 ... 2. Bg2
6. Bird's Opening   1. f4
  • 1. f4 e5!? 2. e6   From's Gambit.
  • 1. f4 e5 2. fxe5 Nc6   Schlechter's Gambit,
7. Queen's Fianchetto Opening   1. b3  (Nimzo-Larsen Attack)
  • 1. b3
8. Baltic Opening   1. Nc3   HeinrichsenDunst, etc.
  • 1. Nc3 d5
  • 1. Nc3 c5
  • 1. Nc3 Nf6
  • 1. Nc3 e5!?
9. Polish Opening   1. b4   (Sokolsky, 1963)  Orangutan.
  • 1. b4 e5 2. Bb2 Bxb4 3. Bxe5   Exchange variation.
  • 1. b4 e5 2. Bb2 Bxb4 3. Bxe5 Nf6 4. c4 O-O 5. a3!
  • 1. b4 e5 2. Bb2 Bxb4 3. Bxe5 Nf6 4. c4 O-O 5. e3 Ee8!
  • 1. b4 e5 2. Bb2 d5 3. Bxe5 Nc6 4. Bb2 Nxb4 5. a3 Nc6 6. e3 Nf6 7. Nf3 Be7
  • 1. b4 b6   Symmetrical.
  • 1. b4 e6
10. Grob's Attack   1. g4   [A Borg defense ("Grob" backwards)  is  1... g5]
  • 1. g4 d5 2. Bg2 c6  
  • 1. g4 e5 2. e3  
11. Van't Kruijs Opening   1. e3!?
  • 1. e3 d5 2. d3   Anna Crumling's  Cow Opening.
  • 1. e3 e5 2. e4   Reversed Open Game  (i.e., playing defense as White).
  • 1. e3 f5 2. e4   Reversed From's Gambit.
  • 1. e3 e5 2. Qh5 Nc6 3. Bb5
12. Mieses Opening   1. d3
13. Anderssen's Opening   1. a3   (Anderssen-Morphy, 1858).
14. Saragossa Opening   1. c3   (Zaragoza, Spain, 1919). 15. Clemenz Opening   1. h3
16. Barnes Opening   1. f3
17. Ware Opening   1. a4   Meadow Hay Opening   (Preston Ware, 1821-1890).
18. Desprez Opening   1. h4
19. Durkin Opening   1. Na3   (Sodium Attack).
20. Amar Opening   1. Nh3   (Ammonia Opening).  Yes,  it stinks!    Cartoon
  • 1. Nh3 e5 2. f3 d5 3. Nf2.   Krazy Kat.
  • 1. Nh3 d5 2. g3 e5 3. f4?! Bxh3 4. Bxh3 exf4   Paris Gambit.

A given situation can often be obtained by executing the same moves in different orders.  In that case,  the resulting variations are said to be  transposed  from each other.  For example,  the  Nf3  variation of the Scandinavian defense transposes to a Zukertort opening:

1. e5 d5 2. Nf3       -->       1. Nf3 d5 2. e5

Paul Rudolf von Bilguer (1815-1840) initiated the  Handbuch (1843, 1852, 1858, 1864, 1874, 1880, 1891, 1912-1916).
 
Chess.com   |   All Chess Openings by First Move   |   Transposition   |   Transposition tables  (dynamic programming)
List of chess openings   |   Irregular chess openings   |   Hypermodernism   |   Schools of Chess
 
Chess openings  &  Study plan  (Chess.com).
Top 10 Chess Openings of Garry Kasparov  by  Yury Markushin  (TheChessWorld, 2017-01-13).
 
First moves in chess databases:   365Chess.com   |   ChessGames.com
 
Chess Openings for Engine Competition
 
Top 7 Aggressive Chess Openings (9:38)  by  Kevin Butler  (TheChessWebsite, 2014-09-03).
Harry Nelson Pillsbury (1872-1906):  The man who invented  1. d4  (10:16)  Agadmator   (2017-09-01).
Know your openings (22:51)  by  Alejandro Ramírez  (Saint Louis Chess Club,  2015-05-02).
Understand your Openings | Road to 2000 (51:06)  by  Caleb Denby  (Saint Louis Chess Club,  2019-02-27).
 
7 Weird Chess-Opening Names  (chess.com, 2015-03-23).
 
The Englund Gambit (35:33)  by  IM Levy Rozman  (GothamChess,  2021-05-19).
 
Beginner's Chess openings tier list (41:43)  Levy Rozman  &  Hikaru Nakamura  (GMHikaru,  2020-07-31).
 
The 7 WORST Chess Openings (22:26)  by  NM Nelson  (Chess Vibes,  2022-04-24).
 
6 opening traps named after animals (20:44)  by  NM Nelson Lopez  (Chess Vibes,  2022-04-24).
 
The 17 London Opening Traps (28:11)  by  NM Nelson Lopez  (Chess Vibes,  2022-04-24).
 
The dragon opening is named after the Draco constellation  by  vaishakh1000  (Reddit,  2022-08-06).


(2021-12-20)   Ragozin Position
A position commonly reached from  several  opening lines.

Reaching the same position through the same half-moves played in different orders is of course a common thing,  called  transposition  in chess jargon.  After the second move,  this is the rule rather than the exception.  For cultural and historical reasons,  the Ragozin position is normally studied only under the name of  Ragozin defense  as a variation of the  Queen's Gambit Declined  corresponding to the first of the lines enumerated below,  to which other transpositions usually refer to;

  • 1. d4 d5 2. c4 e6 3. Nf3 Nf6 4. Nc3 Bb4   Queen's Gambit Declined.
  • 1. d4 d5 2. Nf3 Nf6 3. c4 e6 4. Nc3 Bb4
  • 1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Nc3 Bb4
  • 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 d5   Nimzo-Indian, 3 knights.
  • 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 c5

No matter how the position is reached, it can then be played several ways:

  • 5. Bg5 dxc4 6. e4   Vienna Variation.

Viacheslav Ragozin (1908-1962)
 
The Ragozin defense (Chessable.com)
 
Playing the Ragozin (2016)  by  Richard Pert.


(2018-09-02)   Combinatorics of Chess

Number of possible chess configurations after  n  plies.
n01234567 OEIS
Diagrams120400536271852815677926061094305342 A019319
Positions120400536272078822518941768196400068 A083276

chess diagram  merely describes the positions of the various pieces on the chessboard.  whereas a  chess position  also includes information about  castling  and  en passant  privileges.  (The terms  configuration  or  situation  are used here to cover either concept indifferently.)

The two enumerations start to differ after two full moves  (four plies)  when a white pawn is on rank  5  with a black pawn to its immediate right or left  (and any other black move played elsewhere).  In this case,  White has  en passant  privileges for the third move  only when  that side pawn arrived there on the  second  black move.

complete position  consists of a  chess position  and a  ply number  (odd only when it's White's turn to play).  Transposition tables  in chess-playing software typically contain only positions with ply-parity  (indicating whose term it is to play)  although complete ply information would be needed to properly deal with draws by repetition and apply the  50-move rule  (and/or the new  automatic  75-move rule,  officially introduced in 2014).

In the case of the above enumeration,  the ply number is given  a priori,  so the mere  position  fully determines the  complete position.

 Andre Dunican Philidor 
1726-1795

Les pions sont l'âme des échecs.
André Danican  Philidor  (1726-1795)

Enumerating one-sided pawn configurations :

Pawns can occupy only 6 ranks  (the first and last one are ruled out).  If they were only alloed to go straight,  there would only be  C(8,p) 6p  configurations of  p  pawns  (0≤p≤8).  This adds up to  78 = 5764801  possible configurations.  That number is thus a  lower bound  to the total number of configurations.  (One quick way to obtain this resulat is to consider that there are 7 possibities for each file; either no pawn or a single pawn in one of the 6 allowed ranks).

On the other hand,  we can obtain an upper bound by allowing the  p  pawns distinct positions anywhere in the 48 squares where they can be.  That's  C(48,8) = 377348994.

Thus,  the correct number is between 5 and 378 millions.

Actually,  the  p  pawns may have been involved only in a total of  c  captures  (c≤0≤15-p).  Some leftward, some rightward.  Our first lower bound is actually the exact count when  c = 0.

 Come back later, we're
 still working on this one...

Upper bounds to the number of possible chess diagrams

To find a fairly tight upper bound, we start by the exact number of ways to place the two kings so that they're not next to each other.  Then, we'll place all possible remaining pieces on the other 62 square.  This does leave some impossible postions  (for example, when both kings are in check)  but relatively few.  Also, there are diagrams which are notoriously unreachable for nontrivial reasons.  Most notorious;y the two-knight checkmate.  (what could the previous move have been?)

  • A white king on one of the 4 corners rules out 4 squares for the black king.
  • A white king on the rest of the border (24 squares) rules out 6 squares for the black king.
  • A white king on one on the 36 inners squares disallows 9 squares for the other king.

All told, the number of ways to place the two kings on non-adjacent squares is:

4 × (64-4)  +  34 × (64-6)  +  36 × (64-9)   =   3612

That's a 10.4% improvement on the number of ways to place the two kings on twi different squares d  (64 × 63  =  4032).

 Come back later, we're
 still working on this one...

Shannon number  (Claude Shannon, 1950).       Numericana :   Combinatorics
 
Statistics on chess positions?  by  François Labelle  (2017-08-19).
 
An upper bound for the number of chess diagrams without promotion by Daniel Gourion (2021-12-17).
 
How many chess games are possible? (12:10)  by  James Grime  (Numberphile, 2015-07-24).


 Gerard Michon (2021-12-18)   Single-byte encoding of most half-moves in chess.
This code includes the name of the moving piece.

The encoding scheme described below is able to specify any legal move  (and a number of illegal ones)  for a given player in a known diagram,  sssuming only that there are  fewer  than four pieces of each type.

In pathological cases exceeding that limit,  the scheme may call for two bytes to specify some oves involving a piece with too many twins.

Each side always has only one king and never more than eight pawns.  Each piece other than the rook ansd pawn is identified by a numebr from 1 to 3 among its twins as they occur on the board reading line by line from top to bottom and right to left.  It does take some thinking to pack all the information required in a single byte in such a way that it can be decoded without ambiguity.  There is not enough room to allow for more than 3 pieaces of each kind.  The leftovers in the decoding process are used to encode special moves like castling, resigning and offering a draw as well as an exception hanling mechanism to allow escape to a second byte of code whan abolutely necessary in the aforementioned pathological cases with many pieces of the same type  (an 10-bit code is then used whose top two bits are embedded in the leading byte).

Different single-byte half-move codes :
  B7B6B5B4B3B2B1B0 Second-byte extension
Queen 1 1-3 b/r D 1 to 7 10-bit codes  are only used when there are 4 or more like pieces.
King 1 1 K-Move 000
10-bit 1 0 1 E9 E8 000 E7E6E5E4E3E2E1E0
Pawn 1 00 Move 0-7 Under-
promotion
Piece Move
Rook 0 1-3 1D 1 to 7 Usual promotion to a queen is just denoted by an ordinary (nonzero) move to the last rank in a single byte.  A zero move just indicates the presence of an extra byte containing the actual (nonzero) code and the code for the piece you're under-promoting to.
 
The only other use of a zero-code move is to denote a two-square jump as the initial move of a pawn.
Bishop 0 1-3 0D 1 to 7
Comment 0 1 0-7 000
Resigns 0 0 1 1 1 000
Draw 0 0 1 1 0 000
O-O-O 0 0 1 0 1 000
O-O 0 0 1 0 0 000
Knight 0 00 1-3 N-Move
Result 0 00 00 1 to 7
End 0 00 00 000

K-Move Codes
011010001
100 000
101110111
N-Move Codes
010001
011000
 
100111
101110
Pawn Moves
00 W
h
i
t
e
011011
 
B
l
a
c
k
011011
00

Distance traveled along a direction (D) for long-range pieces is a nonzero number (1-7) understood modulo 8  (thus possibly as a negative number when the positive interpretation falls off the board.  Thus, for the horizontal motion of a rook, the following code applies where only one occurence of the two possible meaning of a 1-7 code is valid, as the other is off the board.

Horizontal rook-move shows how only one value of a 1-7 displacement is valid.
001010011100101110111   001010011100101110111
  Example, when on file "c": abcdefgh  

Vertical rook-move shows how only one value of a 1-7 displacement is valid.
001010011100101110111   001010011100101110111
  Example, when on file "3": 12345678  

Likewise, there are two kinds of bishop moves:

  • Ascending (D=0):  Vertical and horizontal displacements are equal.
  • Descending (D=1):  Those two displacements are opposite.

. The board is always shown as White normally sees it:  White pawns only move upward, black pawns go downwards.  There are three ordinary (nonzero) types of pawn moves.  All one square forward possibly diagonally (to the left or to the right) in case ofcapture.  The zero move is either a two-square jump from the starting rank or an under-promotion  (a pawn being promoted to any piece other than the usual queen).  In that case, the next byte contains two bits specifying the true (nonzero) pawn move and two bits encoding the desired piece  (rook, bishop or knight).  That's to say nine possibilities encoded in four bits  (and four unused bits).

Extra byte is almost never called for :

The special extended "10-bit code" contains 2 bits of data in the leading byte and 8 bits from the following byte.  Four of those bits are used to specify which of the 16 pieces is to be moved  (each player has at most 16 pieces on the board).  The other 6 bits specify the desired relative displacement modulo 64.  As this can't be zero, the extra byte is never zero and we can be sure that a zero byte cannot occur in an encoded sequence of chess half-moves,  except as an endmarker.  This makes it trivial to skip an entire sequence of moves to access the rest of the data.

Can we do better ?

Yes,  very much so.  From any chess position  (including diagram, turn, castling and  en passant  information)  we can use a fixed procedure to generate all the possible legal moves and simply specify the index within that list of the move to be played.  Even better,  we don't need to specify a fixed number of bits for each half-move but simply encode the whole sequence of moves as a  (large)  number  N.  from a given position,  we may generate the  p  possible moves.  The index in that list of the first move to play is  N mod p  and the code for the rest of the sequence is  (N-m)/p.  An so on until the code for the remaining sequence is  0  (no more moves to play).

Acknowledgment :   In a  draft put online on 2002-07-26  (revised 2003-12-26, 2006-07-19, 2006-10-22 and 2013-02-26)  Norman Brenner proposes to encode a chess half-move in a single byte (8 bits).  Unfortunately, his method uses one more bit than necessary to describe the moves of long-range pieces  (bishop, rook and queen)  which makes his claim  (up to 4 pieces of the same kind on the boad)  utterly impossible to achieve.  Even with our more compact coding for long-range pieces, a single it's impossible to handle more than 3 pieces of the same kind in a single byte. uses 6 bits to describe move of a queen


 Gerard Michon (2022-01-14)   Fairy byte  encodes moves without naming pieces.
A more practical approach is more flexible, with improved generality.

Different single-byte half-move codes :
  B7B6B5B4B3B2B1B0 Second-byte extension
Queen 1 1-3 b/r D 1 to 7 10-bit codes  are only used when there are 4 or more like pieces.
King 1 1 K-Move 000
10-bit 1 0 1 E9 E8 000 E7E6E5E4E3E2E1E0
Pawn 1 00 Move 0-7 Low Queening Piece Move
Rook 0 1-3 1D 1 to 7 Usual promotion to a queen is just denoted by an ordinary (nonzero) move to the last rank in a single byte.  A zero move just indicates the presence of an extra byte containing the actual (nonzero) code and the code for the piece you're under-promoting to.
 
The only other use of a zero-code move is to denote a two-square jump as the initial move of a pawn.
Bishop 0 1-3 0D 1 to 7
Comment 0 1 0-7 000
Resigns 0 0 1 1 1 000
Draw 0 0 1 1 0 000
O-O-O 0 0 1 0 1 000
O-O 0 0 1 0 0 000
Knight 0 00 1-3 N-Move
Result 0 00 00 1 to 7
End 0 00 00 000

The term "fairy chess" was coined in 1914 by the musician, poet and chess columnist  Henry Tate (1873-1926).
 
Ferz (shatranj)   |   Amazon   |   Empress   |   Princess (archbishop)   |   Wazir   |   Camel
 
Grasshopper  (1912)   |   Nightrider or knightmare  (1925)   |   Thomas_Rayner_Dawson  (1889-1951)


(2018-08-24)   Systems:  Formations involving several pieces.
Opening systems may be valuable even if incompletely executed.

All systems are difficult to classify in standard books of openings because,  by definition,  they are routinely  transposed  into several lines.

  • London system.
  • Stonewall system.
  • Colle system.
  • Tartakower-Makogonov-Bondarevsky System  (TMB).
  • Hedgehog system.

 Come back later, we're
 still working on this one...


(2018-08-15)   Maxims and Aphorisms
A tiny collection of chess proverbs and famous quotes.

Whoever answers before pondering the question is foolish and confused.
Proverbs 18:13

  • If you see a good move, try to find a better one.  (Damiano, 1512)
  • The threat is more powerful than the execution.
  • Knight on the rim is dim.
  • A pawn on the seventh is worth two on the fifth.
  • A pawn on the seventh is worth a rook.
  • Brilliancy can only occur if the opponent makes a mistake.  (Rubinstein)


(2021-12-14)   Textbook Endgames
Foolproof recipes devised to solve some standard endgame situations.

100 Endgames You Must Know (2008)  by  GM Jesus de la Villa (1958-).
 
Important Endgames that People Mess Up (51:02)  by  IM Eric Rosen  (Saint Louis Chess Club,  2017-01-18).
 
Pigs of the Seventh Heaven (47:44)  a.k.a., Castlemania (Khare 2022)  by  IM Eric Rosen  (Saint Louis,  2017-05-31).
 
King & Pawns Endgames (21:14)  by  IM Levy Rozman  (GothamChess,  2020-12-07).
 
King, Bishop &Knight vs. King (21:14)  by  IM Kevin Gong  (KevinGongChess,  2013-11-30).
 
King, Knight & Bishop vs. King (56:24)  by  GM Ben Finegold  (Atlanta Chess Club,  2018-11-11).
 
Checkmate with two bishops (6:22)  by  Jeetendra Advani  (Chess Talk, 2017-12-02).
 
Checkmates with bishops and knights (43:03)  by  GM Varuzhan Akobian  (Saint Louis, 2017-02-24).
 
Two Knights vs. Pawn (5:25)  by  Matt Pullin  (GreenCastleBlock, 2008-02-14).
 
Chess_endgame (Wikipedia).


(2007-07-01)   Nalimov computer tables for endgames with few pieces.
Tabulating all positions is an efficient way to solve an endgame perfectly.
 
 Mate with Bishop
 and Knight 

If the total number of game positions is small enough, then each of them can be allotted a small computer record in an explicit table.  The entire game can then be solved efficiently by analyzing that table  top-down  (first completing the records corresponding to final positions, like checkmates).  For the game of chess, this is practical only in endgame situations, when only very few pieces remain on the board.

database  is a set of stored key/value pairs, where only a small portions of the possible keys exist  (for example, not all possible surnames exist in a database of people whose names are used as "keys").  By contrast, a  tablebase  includes (almost)  all  keys.  The key itself need not be stored in a tablebase; it's merely used to compute the unique numerical address where the information corresponding to that key is located.  In game tablebases, the game position is the "key" used to access the value recorded in the tablebase.

By contrast, in a data base, only a tentative address can be computed, based on a so-called  hash-code  which a key may share with many other possible keys.  The location computed from the key's hash-code is merely a starting point where a whole list of keys can be found (with their associated recorded values).  When a database is queried for a key, the query key must be compared with the stored keys.  The size of a database containing n different keys is thus more than  n lg n  bits.  (A tablebase which associates a single bit to each of n possible keys has a size of only  n bits.)

Perfect play  is defined as achieving victory as fast as possible, or delaying defeat as much as possible.  A full analysis of the game is normally possible only by recording the length of a perfect game for each tabulated position  (the position is a first-player win when that length is odd, it's a first-player loss otherwise  (the issue of ties is discussed below).

A computer database which gives the number of half-moves to the end of a perfectly played game is called a  Nalimov table.  It's easy to play perfectly by looking up such a table:  Play into the smallest even position if you can, otherwise play into the largest odd position.  A special label must be assigned to ties which is adequately defined as an odd number larger than any other...  (for example 255, if Nalimov records consist of a single byte).

There is no notion of "perfect play" for a game which ends in a tie.  Such a game is merely considered equivalent to a game which goes on forever because neither player can force a victory.  Yet, it's possible to refine Nalimov values to distinguish between a tie  "by the book"  (which tells that an undecided game is over) having the highest odd value and other ties which have odd values just below that  (but above any other odd values corresponding to true first-player wins).

Error-free play  (as opposed to perfect play)  can be defined as what happens when neither player gives up victory when it's available to them.  It is not required of the winner to force a quick conclusion.  A practical "tie" may even result if victory is postponed indefinitely  (a win may thus be transformed into a tie by the actual rules of chess which limit the number of capture-free moves).
 
Compact bit-wide tablebases, known as  bitbases,  are sometimes used in actual chess-playing programs as "oracles" which help make error-free decisions in the endgame.  A  single bit  is assigned to each position whose value is zero (0) if and only if it is a first-player loss.  The value "1" corresponds to a first player win if and only if it has at least one option labeled "0"  (otherwise, the "1" indicates a tie).
 
A bitbase  (for mere error-free play)  is normally obtained by extracting the relevant information from a complete Nalimov table.

Eugene Nalimov  was born in Novosibirsk in 1965.  He joined Microsoft as a programmer in 1997,  he later joined the Seattle-based  Context Relevant  startup  (called  Versive  since 2017).  Nalimov started writing tablebases generators for chess endgames in 1998.  He was honored for that work by  ChessBase  at their 2002 convention,  in  Maastricht.

Example: The Knight and Bishop Endgame

The basic table base (TB) only needs to consider the positions where the bishop is on one of the 16 topmost white squares.  Ignoring obvious illegal positions (e.g., several pieces on the same square or adjacent kings) the other pieces can be on one of 64 squares and it can be the turn of either Black or White.  All told, the size of the TB, at one byte per position, is fairly small:

2 . 16 . 64 . 64 . 64   =   8 MB

Each of those bytes just contains the number of moves to mate.

Well beyond what humans can compute :

NNK vs K  NNK vs K  Ignoring the 50-move rule, starting from this position White can mate Black in 94 moves.  The  only  winning move is Ke3!!

Kde-e3 !!   Kh2-g3 

Against another reply,  White can mate in at most 10 moves  (instead of 93).

Endgame Tablebase   |   Just one of 17,823,400,766 positions  (Chess News,  2002-01-04).
 
Checkmate with two bishops (6:22)  by  Jeetendra Advani  (Chess Talk, 2017-12-02).
 
Chess Endgame Database  by  by Stefan Meyer-Kahlen  (Shredder).
 
8 Longest 7-Man Checkmates  by  by Stefan Meyer-Kahlen  (Lomonosov Tablebases, 2012).
 
Syzygy endgame tablebases  by  Ronald de Man (6 men, 2013)  and  Bojun Guo (7 men, 2018).


(2021-21-31)   King and knight vs. king and pawn.
Color matching required to mate a cornered king with a knight.

In the folloing diagram, when the white knight is on a numbered square opposite to the color of the cornered black king it can mate it in the number of moves so indicated.  Mate can only be delivered from a last move from the only square numbered "1" (c1) to the unique square numberd "0" (b3).  When on c1, the knight puts the king in check,  so the only black move available is to advance the pawn to a2,  cornering the king which is checkmated when the knight moves to b3.  If Black were to choose to advance the pawn before being forced to do so that way,  the white knight would be on a dark odd-numbered square and could deliver mate by moving directly to b3.

Otherwise,  the strategy is simply for the knight to move from a numbered square to a numbered square with a lower number.  Moving to another numbered square simply delays the mate.  The knight can ultimately deliver checkmate if and only if it moves from the same solor as that of the black king.  If the knight is on the wrong color,  there can never be a checkmate even if Black cooperates.  If the knight isn't on a numbered square,  Black will have an opportunity to force stalemate by advancing the pawn when a2 is free and the knight is too far to check.

 K N vs K P mate
 8 
7 44
6 444
5 534
4 4634
3  Black Pawn 0 24
2  Black King  White King 52
1 616
  abcdefgh

The above is the basis for some chess puzzles composed before the first publication of  Bonus Socius  compilation  (around 1266).  The changes in the rules of chess since that time didn't affect kings, rooks, knights and pawns  (except on their first moves).

Also, the single line given below  (which leads to a different mating position)  can be used when the pawn is as high as a4.  No such thing exists for a5 or above,  because that would entail a possibilty for the pawn to capture the knight or for the black king to escape to b4.

 K N vs K P puzzle   If N starts from a6, c6, d5 or d3 (shown left).

Mate in 3

Nb4!  a3
Kc1   a2
Nc2#
 K N vs K P mate

Checkmating Chases :

The above is perhaps the ultimate example of a chase ending in checkmate which the winner can only lengthen and the loser only shorten.  Few chases has this feature and it's difficult to define precisely what a chase is but you know one when you see one.  Here are examples from real archived games:

  • #2FdzU (1847) .  27...Qh2+? would be a mistake instead of 27...Bh2+!

 Come back later, we're
 still working on this one...

Bonus Socius  (before 1300).


(2010-01-28)   Static Evaluation Function
Evaluating quiescent positions is an art form.

Relative values of chess pieces according to various authors :
  PNBB'RQ
André Danican Philidor, 1777 1.00  3.00  3.50  4.00  5.50  10.00
Peter Pratt, 1799 1.00  3.00  3.00  3.00  5.00  10.00
Larry Evans 1958 1.00  3.50  3.50  4.00  5.00  10.00
Maurice Beaucaire, 1967 1.10  3.00  3.00  3.50  5.00  10.00
Bobby Fisher, 1972 1.00  3.00  3.25  3.75  5.00  9.00
Garry Kasparov, 1986 1.00  3.00  3.15  3.65  4.50  9.00
Hans Berliner, 1999 1.00  3.20  3.30  3.80  5.10  8.80
Larry Kaufman, 1999 1.00  3.25  3.25  3.75  5.00  9.75

With the only possible exception of the earliest one  (Pratt)  all the above authors have pointed out that a pair of bishops is worth more than twice the value of a lone bishop.  When pressed to quantify that bonus, they reluctantly say it's about half a pawn  (50 centipawns).  In the above table we added that bonus  (0.5 by default)  to the value of the second bishop, denoted B', which is mathematically equivalent.

 Come back later, we're
 still working on this one...

A knight and a bishop are better than a rook and a pawn.  Three minor pieces are better than a queen.

Endgame evaluations :

A radical method would be to consider the ability to mate of certain combinations of pieces against others,  measured by the maximum number of moves needed to resolve the situation to a mate  (as obtained from  Endgame tablebases):

Relative value of chess pieces   |   Evaluation function   |   Compensation   |   Hans Berliner (1929-2017)


(2010-01-28)   Minimax Search
Minimize your opponent's gain, maximize your own.

 Come back later, we're
 still working on this one...


(2010-01-28)   Alpha-Beta Pruning
In a minimax search, some alternatives need not be explored at all.

 Come back later, we're
 still working on this one...


(2010-01-28)   Hash Tables
How to avoid exploring the same position more than once.

 Come back later, we're
 still working on this one...


 One of 4 possible positions 
 at the end of a 2-move game.  (2010-01-27)   Short Games
Checkmates in the opening moves.

1.  Fool's mate  (2-move mate) :

This is the shortest of all chessgames.

There are  8  variations which result in a position similar to the one depicted at right, where White is checkmated.  They differ by the order White moves his two pawns and also by two possible choices for moving the central pawns of each player  (one square or two squares).

The locution  fool's mate  is sometimes used as a generic term to denote any  very early checkmate, especially the following one:

 How Mikhail Tal (Black) got defeated, 
 at age 9 by his brother (White).  Riga, 1945.  

2.  Scholar's mate (Queen raid)

At age 9, Tal, lost to his brother thusly:

1. e4   e5     3. Qh5  Na6
2. Bc4  Bc5    4. Qxf7#

This mate is often attempted among newcomers.  The French call it  le coup du berger  which translates literally as  Shepherd's mate, as do the names of that checkmate in several other languages, including Spanish, German, Dutch and Portuguese.

The  fool's mate  and  scholar's mate  may well be as old as chess itself but they were apparently not mentioned in print before the seventeenth century, as they found their rightful place in the early classification proposed by one  Arthur Saul  in  "Famous Games of Chesse-play" (1614).

Counting the number of 4-move games ending in a  scholar's mate  can be an interesting exercise:  The game may end with  Qf3xf7#  (e.g., after the infamous Napoléon opening)  or  Qh5xf7#  (as above).  In either case, White can play in 4 different ways  (opening with either e3 or e4, then moving either the bishop or the queen).  Each sequence makes different "compatible" moves available to Black.  If the black queen moves, she must move back.  To allow the mating move, the white queen's path must be clear and  f7  must be unprotected...

How to beat the four-move checkmate (4:36)  by  ChessVision.net  (2008-01-28).
1. e4 e5 2. Qh5 Nc6 3. Bc4 g6 4. Qf3 Nf6 5... Nd4
 
Checkmate on move 7, by two hanging pieces (Lichess #rVKbx, rated 1641).


(2021-12-11)   The quintessential chess puzzle:  Find mate in N moves.
The challenge may be to  prove  one can checkmate in  N  moves or less.

Checkmate  is the situation when the king is in check and cannot get out of it.  That would mean that it couldn't avoid capture on the next move if the games was allowed to go on.  Under modern rules,  a  checkmate  ends the game.

Originally the purpose of chess was to capture the king, but requiring a proper checkmate makes careless play illegal where a king is captured when it had a way to escape.  Both players are responsible to verify that a checkmate is valid.  Therefore,  being able to recognize checkmate  (and also stalemate)  is a prerequisite to play chess.  It just as basic as learning how the pieces move,  albeit a bit more difficult.  Chess would essentially be the same game it is was allowed to proceed till the actual capture of the king,  as was the case in the old days.  Except that stalemate would still be a win instead of a draw,  as it is today.  (The status of stalemate as a draw makes some endgames more interesting but it's what prevent chess from being a  normal  game;  the qualifier which says that whoever has no legal move loses the game.)

The only recorded outcome in competitive chess is win, lose or draw.  However,  in the world of chess puzzles,  best play  is always meant to force chackmate in as few moves as possible against an opponent doing his best to delay it.

There is absolutely no other measure of the value or beauty of a game of chess beside this.  Ever.  In particular,  the pieces still on the board of a finished game have no value whatsoever.  In fact,  some admire instead the skill of a player who was able to win the game by cleverly sacrificing pieces to achieve checkmate.  One of the most famous example is what's known as the  immortal game.

Here,  White just queened with check.  Clearly Black should have resigned a long time ago.  The challenge for White is to arrive at a checkmate on his third move or earlier.  The problem is to find the winning move (there's only one).

Mate in 3

Mate in 3

1. Bd8+ Kc6
2. Qf6+ KxN
3. Qb6#
 
1. Bd8+ Kc6
2. Qf6+ Kb5
3. Qb6#
 
1. Bb8+ Kc8?
2. Bb6#
 
The third variation ended earlier because Black didn't play well.

Mate in 3

An ancient mate-in-2 puzzle

There's only one solution:  Rg7!!
(It's much easier to mate in 3...)
 
This appears in the  Bonus Socius manuscript  (c. 1266).
 
The puzzle may well be much older.

 Come back later, we're
 still working on this one...

  • #OpPOh:  Top-rated mate-in-1 Lichess puzzle  (2429).
  • #OpPOh:  My "final" mate-in-1 puzzle  (2292).
  • #0e3Xk:  Another mate-in-1 puzzle  (2176).
  • #09nQI:  Mate-in-1 involving pinning  (2010).
     
  • #2WyFZ:  A rare checkmate using underpromotion:  c8=N#

Some Named Checkmate Patterns:   (Mates in 0 moves.)

A colored disk indicates either a piece of that color or a square guarded by a piece of the other color.
Anastasia's mate   Anastasia's Mate
King could also be on h2
(or h3, if the rook is guarded).

Checkmate   |   Named checkmate patterns   |   Bishop and knight checkmate
 
1st Prize, Leilo 1951 (10:01) by Vladimir Korolkov (NM Nelson Lopez, 2022-10-18).


(2021-12-13)   Unconventional puzzle:  Find the worst possible move.

A dirty dozen blunders    (ChessBase, 2004-01-17).


(2018-08-27)   Risky defense against the  Fried-Liver Attack :
Played sharply,  the super-agressive  Traxler counter-attack  can pay off!

Most beginners are exposed to the elementary  fried-liver attack  shortly after learning about the the above  Scholar's mate.  The  usual defense  is:

1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5!? d5

However,  the following analyzed game illustrates a  bold  counterattack which is far from elementary  (to avoid it,  White could play  5. Bxf7+  gaining a pawn).  If White  ever  loses a tempo with  Nxh8  then the game is hopelessly lost when Black plays perfectly!  I'm using this as an example of how a written analysis can be presented:  We show the strongest move of the winning side  (Black here)  for  every  possible reply of the opponent,  except  when the move to be refuted  (Nxh8)  is played.

The paradoxical consequence of the following refutation of  Nxh8  is that the threat on the rook is only  apparent.  At least for  extremely  sharp play...

Conveniently,  the quoted 1967 game doesn't last very long because of the mistakes of White  (starting with  6. Kxf2).  The opponent of Traxler in 1890 didn't take the bait,  which opens up an interesting 17-move game.  Both actual games are  shown in bold,  within the combined  decision tree.

F. Hollingsworth vs. Ron Steensland      [ WARNING: Hand analysis.
(68th US Open, Atlanta, 13 August 1967)             Not finalized. ]

1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5! Bc5! 5. Nxf7!? Bxf2+
   6. Kxf2? Nxe4+
      7. Ke3? Qh4 8. Nxh8?? Qf4+
         9. Kd3 Nb4+ 10. Ke2 Qf2#
         9. Ke2 Qf2+ 10. Kd3 Nc5+! 11. Kc3 Qd4#
      7. Kf3? Qh4 8. Nxh8? Nd4+
  [or 7. Ke2? Qh4 8. Nxh8? Nd4+ (9. Kf1?? Qf2#)] 
         9. Ke3 Qf4+ 10. Kd3 {A: Mate in 7} Nc5+!! 11. Kc3 Nb5+!
            12. Bxb5?? Qd4#
            12. Kb4  a5+!!
                13. Kxc5? Qd4+ 14. Kxb5 Qb6+ 15. Ka4 Qb4# 
                13. Kxb5 b6!
                    14... Ba6#
                    14. Qh5+! Ke7 
                        15. Qh4+ Qxh4 16... Ba6#
                        15. Qg5+ Qxg5 16... Ba6#
         9. Kd3 Nc5+
            10. Ke3? Qf4#
            10. Kc3 Na4+
                11. Kb4 Qe7+!
                    12. a5? Qc5+ 13. Kxa4 Qxc4+
                        14. Ka3 Nb5#
                        14. Ka5 Nc6#Zhang Yuntao
                    12. Kxa4 a5!!
                        13... Qb4#
                        13. a3/c3 d4!
                            14... Bd7!
                11. Kd2 ...
      7. Ke1 Qh4+ 8. g3 Nxg3 9. hxg3 Qxg3+ 10. Kf1 Rf8 (or O-O)
      7. Kg1 Qh4 8. g3 Nxg3 9. hxg3 Qxg3+ 10. Kf1 Rf8 (or O-O)
      7. Kf1! Qf6+ (8... Qf2#) 8. Qf3! Qxf7 9. Kxf7 Rf8 (or O-O)

J. Reinish vs. Karel Traxler
(Hostoun near Prague, 20 March 1890)

   6. Ke2?  Nd4+! 
      7. Kd3? b5!
         8. Bb3 Nxe4!!                     (Queen sacrifice)
            9. Nxd8? Nc5+ 10. Kc3 Ne2+!    (Knight sacrifice)
               11. Qxe2 Bd4+ 12. Kb4 a5+
                   13. Kxb5 Ba6+ 14. Kxa5 Bd3+ 15. Kb4 Na6+
                       16. Ka4 Nb4+ 17. Kxb4 c5#
                       16. Ka5 Nb4+ 17. Kxb4 c5#
                       16. Ka3 Nb4+ 17. Kxb4 c5#
                   13. Ka3?? b4#
               11. Kb4? a5+ (Same ending, one move sooner.)
            9...
         8...
      7. Kxf2? Nxe4+
         8. Ke3 Qh4 9. Nxh8? Qf3+ 10. Kd3 {A: Mate in 7, above.}
         8. Kf1 Qf6+ (9... Qf2#) 9. Qf3! Nxf3
            10. gxf3 Qxf3+ 11... Qf2#
            10. Ke2 Nd4+ 
                11. Ke1 Qf2#
                11. Ke3 (or Kc3) Qf3#
            10... Nd4 11... Qf2#
         8. Ke1
      7. Kf1! Qe7 7. Nxh8? d5
         8. exd5 Nd4  (Recommended by Karel Traxler himself.)
            9...
         8. Bxd5 Nxd5
            9. exd5 Bg4+!?
               10. Kxf2? Qf6+
                   11. Kg3?? Qf4#
                   11. Kg1? Bxe1 12... Nd2#
                   11. Ke3 Qf3+ 12.Kd3 Be2+
                       13. Kc3 Nb5+ 14. 
                       13. Qxe2 Qxe2+ 14. Kc3 Nb5+ 15. Kc2 Bc4+
                           16. Ka4 Bxe5+
                               17. Ka3 
                               17. Kxb5 Qc4+ 18. a5 Qc5+ 19. Ka4 b5+
                                   20. Kb3 Qc4+ 21. Ka3 Qa4#
                                   20. Ka5 b4+ 21. Ka6 Qb6# 
                   11. Ke1 Bxd1
                       12. Kxd1 Qf2
                           13... Qd2#
                           13. Rd1 Qxg2
                               14. Rf1?? Qd2#
                               14... Qf3+ 15. Rd2 Qxd2#
                       12... Qd2#
                       12. Rf1! Qa6! (13... Qd2#)
                           13. Rf2!? O-O ...
                           13. d3 Qa4!
                               14. b2 Nxb2
                                   15. axb2 Qxa1
                                       16. Kxd1 Qxa1
                                       16...
                               14. Ke1 Nc2+
                                   15. Kf2 Qf4#
                                   15. Kg1 Qg4 ...
               10...
            9...
         8...
   6. Kf1! Qe7
      7. Nxh8? d5
         8. exd5 ...
         8...
      7. Ng5!? ...
      7...

The term  Traxler counterattack  is normally used to describe this opening  (especially when the Bishop's sacrifice is accepted,  as in Traxler's original game  6. Kxf2).  However,  in the United States,  it's also called the  Wilkes-Barre Variation  (especially when  6. Ke2  or  6. Kf1  is played)  because it was analyzed by  John Menovsky (1873-1947)  and other members of the  Wilkes-Barre Chess Club  (first established in 1887 and restarted in 1907).  Menovsky published the work in 1934 and 1935 and subsequently discussed the problem with  Kenneth F. Williams (1907-1993)  who would eventually publish a 58-page pamphlet on the topic in 1979,  with only few flaws.

Ken Williams (1907-1993)  was once President of the  Correspondence Chess League of America (which was created in 1909).  His business commitments did not allow him to pursue an over-the-board tournament career which essentially ended with a tie in a competition for the North-American Championship.  He went almost twenty years without playing a single over-the-board game.

Even with the best reply  6. Kf1  White lost  all  the games on record:

  • 1947:  James L Harkins vs. Eugene Levin  (20 moves).
  • 1950:  Lichy vs. Frantisek Blatny  (10 moves).
  • 1955:  Kerner vs. Alfred Brinckmann  (15 moves).
  • 1958:  Cosling vs. Peter Murray  (13 moves).
  • 1959:  Rosenbaum vs. Norman J. Goldberg  (18 moves).
  • 1964:  Julio Kaplan vs. Canoromi  (19 moves).
  • 1964:  Julio Kaplan vs. Canoromi  (16 moves).
  • 1964:  Babitsky vs. Georgy Sapundzhiev  (15 moves).
  • 1964:  Grebenshikov vs. Grigoriev  (22 moves).
  • 1965:  Yakov Estrin vs. Jiri Nun  (16 moves).
  • 1966:  V. Sarkisian vs. Alekper Shahtahtinsky  (18 moves).
  • 1966:  S. Kurkin vs. Yakov Estrin  (25 moves).
  • 1966:  Lueck vs. Endres  (25 moves).
  • 1967:  Wead vs. P. Larsson  (13 moves).
  • 1971:  Tarakanov vs. Solomon Naftalin  (19 moves).
  • 1971:  Siegfried Augustat vs. K. Hentzgen  (19 moves).
  • 1974:  Lothar Schmid vs. Helmuth Lietz  (13 moves).
  • 1974:  M. Sedayao vs. G. Boyd  (13 moves).
  • 1982:  Roger Pernet vs. Colin A. Costello  (17 moves).
  • 1987:  N. Lipowsky vs. Richard Forster  (15 moves).
  • 1989:  Reinhard Fiedler vs. Lothar Simchen  (16 moves).
  • 1996:  Gyorgy Jamrich vs. Jan Dudas  (21 moves).
  • 2001:  Huang Yicheng vs. Zhang Yuntao  (26 moves).  Timeout?

They  all  lost a tempo with  Nxh8,  cornering the knight.

The Opening Boomerang  by  GM  Gregory Serper  (Chess.com, 2016-02-14).
The Traxler Counter Attack  by  Sarah Beth  (Chess.com, 2015-06-13).
CN 9334  by  Edward Winter  (2015-06-16).
Zlatá Praha  (1892-10-14).
What's in a name?   by  MrMip  (ChessForums.org, 2013-06-13).
 
Grandmaster/supercomputer looks at Wilkes-Barre  by  Richard Moody, Jr.  (Chess.com, 2013-07-20).
 
Crushing Counter-Attack against Fried-Liver Attack (4:07)  by  Mato Jelic  (2011-04-04).
Fried Liver Attack (10:58)  by  Kevin Butler  (TheChessWebsite, 2010-05-23).
Traxler Counter-Attack (20:27)  by  Kevin Butler  (TheChessWebsite, 2010-11-20).
Traxler Variation (52:10)  by  GM Ben Finegold  (Atlanta Chess Club, 2018-10-17).
Traxler Counter-Attack (9:28)  by  Jeetendra Advani  (Chess Talk, 2019-06-21).
 
Composition (1983):  The craziest game ever (17:23)  by  IM Levy Rozman  (GothamChess,  2021-08-07).


(2018-08-21)   Miniature Games
Brilliant checkmates in  24  moves or less.

All miniature games last less than  30  moves.  Some will only consider shorter games.  I define a miniature as a game of two dozen moves or less.

Napoléon's Gambit  (Saint Helena, 1820) :

Napoléon Bonaparte (1769-1821)  against  Henri Bertrand (1773-1844):

1. e4 e5 2. Nf3 Nf6 3. d4 Nxd4 4. Nxd4 exd4 5. Bc4 Bc5
6. c3 Qe7 7. O-O Qe5 8. f4 dxc3+ 9. Kh1 cxb2 10. Bxf7+ Kd8
11. fxe5 bxa1=Q 12. Bxg8 Be7 13. Qb3 a5 14. Rf8+ Bxf8
15. Bg5+ Be7 16. Bxe7+ Kxe7 17. Qf7+ Kd8 18. Qf8# 

The Immortal Game  (London, 1851) :

Arguably,  the most famost miniatures of all time was played informally on 21 June 1851,  during a recess of the  first international chess ournament,  between  Adolf Anderssen (1818-1879)  and  Lionel Kieseritzky (1806-1853).  Anderssen,  playing White,  sacrificed his queen,  two rooks and a bishop to deliver a brilliant mate with the three remaining minor pieces  (without capturing a single black piece).

1. e4 e5 2. f4 exf4 3. Bc4 Qh4+ 4. Kf1 b5? 5. Bxb5 Nf6
6. Nf3 Qh6 7. d3 Nh5 8. Nh4 Qg5 9. Nf5 c6 10. g4! Nf6
11. Rg1 cxb5? 12. h4 Qg6 13. h5 Qg5 14. Qf3 Ng8 15. Bxf4 Qf6
16. Nc3 Bc5 17. Nd5 Qxb2 18. Bd6 Bxg1 19. e5!! Qxa1+
20. Ke2 Na6 21. Nxg7+ Kd8 22. Qf6+!! Nxf6 (23. Be7#)

The Evergreen Game  (Berlin, 1852) :

1. e4 e5  2. Nf3 Nc6  3.Bc4 Bc5  4. b4 Bxb4  5. c3 Ba5
6. d4 exd4  7. O-O d3 8. Qb3 Qf6  9. e5 Qg6 10. Re1 Nge7
11.Ba3 b5  12.Qxb5 Rb8  13.Qa4 Bb6  14.Nbd2 Bb7  15.Ne4 Qf5
16.Bxd3 Qh5  17.Nf6+ gxf6  18.exf6 Rg8  19.Rad1 Qxf3
20.Rxe7+ Nxe7  21.Qxd7+ Kxd7  22.Bf5+ Ke8  23.Bd7+ Kf8  24.Bxe7#

The Opera Game  (Paris, 1858) :

Loudly disturbing a representation of  Bellini's Norma  at Théâtre-Italien de Paris on  1858-10-21Paul Morphy (1837-1884) vs. Duke Karl (1804-1877) & Count Isouar as a team.

1. e4 e5 2. Nf3 d6 3. d4 Bg4 4. dxe5 Bxf3 5. Qxf3 dxe5
6. Bc4 Nf6 7. Qb3 Qe7 8. Nc3 c6 9. Bg5 b5 10. Nxb5 cxb5
11. Bxb5+ Nbd7 12. O-O-O Rd8 13. Rxd7 Rxd7 14. Rd1 Qe6
15. Bxd7+ Nxd7 16. Qb8+ Nxb8 17. Rd8#

Réti's Mate  (Vienna, 1910) :

Richard Réti (1889-1929)  against  Savielly Tartakower (1887-1956):

1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nf6 5. Qd3 e5?
6. dxe5 Qa5+ 7. Bd2 Qxe5 8. O-O-O Nxe4? 9. Qd8+!! Kxd8
10. Bg5+ Kc7 11. Bd8# (or 10... Ke8 11. Rd8#)

Michelle Khare's  first lesson :

A quick staged game (scripted or not) between  Michelle Khare  (500)  and one of her first chess coaches, Levy Cozman (2400) wearing a blindfold.

1. b3 e5  2. Nc3 Bc5  3. a4 d5  4. Nf3 e4  5. Ne5 Qf6
6. f4 Qxf4  7. Bb2 Qf2#

The Original Immortal Game (7:11)  by  Antonio Radic  (Agadmator, 2017-09-01).
Homer Simpson vs. Marge Simpson (3:41)  by  Antonio Radic  (Agadmator, 2017-09-01).
 
Game of the Century:  Bobby Fischer vs. Donald Byrne (24:52)  by  Kevin Butler  (TheChessWebsite, 2010-07-18).
 
5 chess games you must lnow (36:12)  by  IM Levy Rozman  (GothamChess,  2022-01-10).
 
Short Chess Games by Serguei Vorojtsov:   | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |


(2010-01-29)   Sam Loyd's Chess Puzzles
Toying with chess positions which can't arise in actual games.

The American columnist  Sam Loyd (1841-1911)  devised many clever puzzles based on the rules of chess which have no relevance to actual play.

Lone black king on h4  (against 16 white pieces).  Mate in 3 moves.  The same problem for other positions for the black king is less easy to analyze.  Tabulated below are the number of moves needed to mate, according to  Fritz 8.  In this context,  e4  is almost always the strongest move; often the  only  strongest move, as indicated by the exclamation mark (!)...  d4  is second best.

Full White Starting Lineup against Lone Black King
abcd efgh
 8  e4! (#8)e4! (#8)e4! (#9)d4! (#9) e4! (#9)e4! (#9)e4! (#8)e4! (#7)
 7  abcd efgh
 6  abcd ee4! (#9)gh
 5  abce4 (#10) e4! (#9)fgh
 4  e4 (#6)e4! (#8)e4! (#7)e4! (#8) d4! (#9)d4 (#9)e4! (#6)d4! (#3)

The Excelsior Problem  (1861).  Mating with the least likely piece.


(2022-03-17)   The  Botte de Nevers  of Chess  (Maja's botte).
Pull-and-fork  (attraction sacrifice).  A startling 3-move combination.

This appears in about 2% or 3% of  Chess Tempo  tactical puzzles.

A sacrificial piece moves next to the king  (usually  grabbing  something in the process, but not always).  As the king takes the bait,  it's then  forked  with the true target.  The king may be forced to takes the bait but it may not be.  In the latter case,  when the rest of the  botte  would result in an exchange of equal pieces,  the opponent choice is irrelevant to the puzzle,  which may thus be truncated at that point  (as illustrated by  #73015808.  #48729,  #51993  or  #55364, taken from a game resigned after the botte started with 2.Rxe7)  Examples  (in order of ratings, at the time of writing):

  • 1052.3: #92220.  Grab knight, trade queens.
  • 1061.0: #47447.  Grab knight, trade bishops.
  • 1120.6: #142245.  Grab bishop, trade rooks.
  • 1132.8: #88542.  After 1.Qh8+ Kg6, grab knight, trade queens.
  • 1156.2: #82048296.  Grab knight, trade queens.
  • 1164.2: #106919.  Grab knight, trade queens.
  • 1168.0: #120318328.  Grab knight, trade rooks.
  • 1175.7: #91387394.  Grab bishop and trade rooks, then knights.
  • 1210.7: #61195006.  3...Rxd5!  wins B, protects N and is bait for botte.
  • 1248.5: #121313.  Trade queens, win both rooks.
  • 1259.8: #126638529.  Grab knight and trade queens.
  • 1260.3: #180597.  Grab knight (2.Rxb5) to trade rooks.
  • 1262.6: #54486.  1.Rh7+ is bait for botte.  NxB still deadly even if 1...Kf8 (messy).
  • 1288.4: #48053.  After 1.Qxg7+ Rf7, grab rook, trade queens.
  • 1334.1: #55763089.  1...Nd5+ 2.Kf2 Rh2+ 3.Bg2 Rxg2+ botte.
  • 1444.5: #135223551.  Grab knight and trade rooks.
  • 1445.6: #71589.  Grab N and trade rooks, with K executing final fork.
  • #57827.  Grab knight, trade queens.
  • #51022881.  Nf6+ forces Kf7, then grab knight to trade queens.
  • #31889732.  Sacrifice Q, win B and get Q back.
  • #143512.  Grab bishop, then Ne3+ if K takes the bait, else Nd4+
  • #113211161.  Grab rook, trade queens.
  • #104601.  Lose rook, win queen.
  • #97907.  Trade rook for queen and Favorable knight and pawns endgame.
  • #56683569  At the end of a non-monotonous exchange.
  • #77556233  Grab knight on second move, trade rooks.
  • #118237  End of a classical exchange.
  • #50078  Pure.
  • #25118  Grab knight, trade rooks (or not).
  • #15731  Q grabs N; trade queens if re-take.
  • #76354246  Grab rook, trade rooks.
  • #111494925  Grab rook, trade queens.
  • #156122  After Rxg2+ 2.Kh1, grab bishop, trade rooks.
  • #98450  Eating last two black pieces.
  • #112847832  One I missed.
  • #77548813  Grab rook, trade queens.
  • #102553896  Grab knight, trade rooks.
  • #142177  Grab knight, trade rooks.
  • #89380484  Grab knight, trade rooks.
  • #59062275  Grab knight, trade rooks.
  • #100541  Grab knight, trade rooks.
  • #118263  Grab knight, trade queenss.
  • #163075  Grab knight, trade queens.
  • #11290645  Grab knight, trade queens.
  • #102652  Grab bishop, trade queens.
  • #54506235  Grab bishop, trade queens.
  • #62466657  Grab bishop, trade rooks.
  • #101847  Trade a rook for a queen.
  • #95796.  Trade rook for queen.
  • #69226443.  Trade rook for bishop and rook.
  • #164881.  Forced trade of one rook for too.
  • #95386  Gambit (1.d5 Kxd5) makes botte possible.
  • #34268  Game over if king takes rook 3.Kxf4 Nd3+.
  • #157249  Botte epilog 3.Kxe4 Nxc3+
  • #171031  King must take sacrificed bishop.
  • #55280099  Queen must take sacrificed rook.
  • #47878587  Take rook to target bishop.
  • #173384  Grab knight to trade queens.
  • #62536347  Grab knight, trade queens.
  • #97010667  Grab knight, trade queens.
  • #72904  Grab knight, trade rooks.
  • #74651  Grab knight, trade rooks.
  • #72891  Grab knight, trade rooks.
  • #156122  Grab knight, trade rooks.
  • #152835  Knight check forces Ke6, then grab bishop.
  • #78798  Rook checks to grab knight and be traded.
  • #53447  Grab knight, trade queens.
  • #106655  Grab bishop with check, trade rooks.
  • #157145 , 1...Rh4+ then fork if 2.Kg1 or botte if 2.Kg2.
  • #167241  Grab knight, trade queens.
  • #100491  Grab knight, trade queens.
  • #75709696  Grab knight, trade queens.
  • #157636  Trade queens to win rook.
  • #52450.
  • #98762.  One premove check by pawn.
  • #152835.  Preliminary check by a knight.
  • #53066105.  Gaining a knight.
  • #79571.  Winning the queen.
  • #72904.  Only one knight remains.
  • #64189576.  Superb.  Winning a lost game.
  • #103687.  Trading queens and keeping a lone knight.
  • #59003.  Trading rooks and keeping a lone knight.
  • #74255.  High-power exchange.
  • #87782643.  Botte start on third move with bishop capture.
  • #95585.  Botte ending 1.Ne6+ Kd7 2.Nc5+ Kc7 3.Rxd6 Kxd6 4.Ne4+
  • #168986.  After preliminary 0...Rxe5 1.Rc8+ Bd8
  • #55364.  Botte starts with 2.Rxe7
  • #38424963.  Queen checks and takes rook which gets in the way.
  • #78441.  Botte starting with 3.Rxg8+ leaves lone white bishop.
     
    Some examples where a  bishop  serves as the forking piece:
  • #87835862.  Grab bishop and trade rooks.
  • #166752.  Grab bishob (2.Rf8+) and trade rooks.
  • #48576012.  After  1.d5 cxd5 2.Rf4+ Ke6  grab bishop to trade rooks.
  • #174527.  Grab bishop, win pawn, trade rooks.
  • #113475821.  Grab bishop, trade rooks.
  • #174501.  Most basic example.
  • #52721891.  Also basic.
  • #32549.  Grab bishop.  Optional rook trade.
  • #171589.  Grab bishop.  trade rooks.
  • #18351.  Grab bishop.  If K takes R, Q is lost.
  • #94360112.
  • #75221.  Substitute for bishop forking two rooks.
  • #89917.
  • #48576012.  1.d5!  The bishop will be forking.
  • #144035.  1.d5!  Grab bishop, win extra pawn.
  • #100550.  Skewer king and bishop as preambule.
  • #96136.  Grab knight, trade rooks.
  • #142360020.  Skewer instead of final fork.
  • #23365.  Skewer instead of final fork.
  • #103802425.  Grab bishop and trade rooks with skewer.
  • #87835862.  King must take rook sacrifice.
     
    It's much rarer to find a  rook  performing the final fork.  One example:
  • #78986.  Trapped bishop is lost with the botte (1...Bxg5) or without (1...Bxc2).
     
    A lone example where the forking piece is a queen:
  • #177540.  Grab bishop and trade rooks,

A lesser variant  (lesser botte)  consists in pulling the target with a sacrifice, instead of the King.

  • 1012.2: #169263.  Grab knight, trade queens.
  • #104972.  Grab knight, trade queens.
  • #103539155.  Grab knight, trade queens.
  • #28648778.  Grab knight, trade queens.
  • #75397  Grab knight, trade queens (then rooks).
  • #128023577.  Grab knight, trade queens.
  • #118567871.  Botte starts with 2.Qxc6.
  • #54607482.  Grab knight, trade queens.
  • #35243732.  Grab knight, trade rooks.
  • #31814.  B grabs N, queen is doomed if it takes back.
  • #3004.  B grabs P, queen must take and is lost.
  • #87337028.  Grab knight to exchange queens.
  • #95758439.  Exchange of queens after knight capture.
  • #11264754.  Queen is baited before royal fork.
  • #71979724.  Yet another example.
  • #95796.  Tougher.  Botte only after 1.Rd6
  • #82048296.  Rxg5 offer rook as bait for rook.
  • #174024.  Grab a bishop and trade queens.
  • #28532651.  Trade queens and win a bishop.
  • #155550.  Grab knight and trade queens.
  • #174516.  Grab knight and trade rooks.
  • #115732361.  Grab Bishop and trade rooks, using bishop.
  • #155447  Grab knight, trade rooks.
  • #70493221  Grab knight, trade queens.
  • #136330  Trade pawn for knight and rook.
  • #175878  Grab knight, trade rooks.
  • #32024050  Grab knight, trade rooks.

Finally,  #163607  is a borderline case of a  passive  botte,  if we may call it that,  where the rook to be sacrificed is already in place,  calling for a  Swischenzug  capture of a bishop.

Not covered here are pulls of pieces besides the king or the target  (e.g., a pawn getting the queen which grabbed the knight in  #163052)  or the rarer  push-and-fork  trick illustrated by  #62490  or the nice  #123150068  (where both possible replies to  1,Rg8+  allow the fork  2.NXC5+  which wins the rook).

I named this after the first person (Maja) with whom I shared (2022-03-17) my observation that the thing is so prevalent in tactical puzzles  (maybe, 2% or 3% of them).  She gives medical advice about weight loss and I mentioned my related quantifiable experiment with rated tactical puzzles as a test-tube for addiction.  She then revealed that she once competed in Chess at the national level in France...  As the dinner we were attending was drawing to a close,  the dual-topic discussion was cut short  (for now).

Exchanges   |   The Exchange


(2010-01-28)   Opening Traps
Well-known deadly traps in the opening game.

Ruy López, Berlin defense; The "fishing pole" black trap  (1, 2, 3, 4)

Trap in the Trompowsky attack

Ryder Gambit (Halosar trap).

Stafford Gambit.

Tennison Gambit.

Lasker Trap.

 Come back later, we're
 still working on this one...

700 Opening Traps  by  Bill Wall  (2010).
 
7 Best Chess Opening Traps (18:28)  by  GM  Igor Smirnov  (Remote Chess Academy, 2017-12-27).
5 Best Traps in the Italian Game (43:53)  by  GM  Nadya Kosintseva  (iChess.net, 2017-10-03).
10 Fastest Chess Opening Traps (32:07)  by  FM  Sebastian Fell  (iChess.net, 2017-08-04).
10 Deadliest Chess Opening Traps (18:37)  by  Yury Markushin  (Chess Channel, 2017-04-10).
Bobby Fischer's 3 Best Chess Traps (40:07)  by  IM  Valeri Lilov  (iChess.net, 2017-10-20).
The Budapest Traps (28:41)  by  AGM  Gunjan Jani  (GJ Chess, 2012-06-11).
Damiano blunder (28:41)  1.e4 e5 2.Nf3 f6?? by  IM Sagar Shah  (ChessBase India, 2012-06-11).
One of the most practical Chess trap  by  5Head-Chess.


(2018-08-09)   Elo Rating System
Rating player skills in a zero-sum game.

One key aspect of the Elo rating system is that the rating only change as the outcome of a game but the sum of the ratings always stays the same.  Whatever one gains, the other loses.

An often overlooked consequence of this, is that the average rating of a fixed pool of players never changes.  That average may only vary as new players enter the pool or old players leave it as they retire or die.  To prevent the average rating from varying over time.  the regulator  (e.g., FIDE in the case of Chess)  should estimate as accurately as possible the average of departing players and attribute that average as the starting rating of new players.  Otherwise,  the average rating changes over time not because players are getting better or worse but simply because the regulations for the starting ratingd of newcomers drive it lower or higher.  Nothing else.

On chess.com when you sign up,  they ask you if you are a beginner, intermediate, advanced or expert and just ask you an initial rating of 1200, 1400. 1600 or 1800 accordingly.  The initial puzzle rating of everybody is 1000.

On Lichess, the initial puzzle rating of everyone is 1500.

In the case of Chess.  we can also hudge the ski;; from games of record and adjust the entry regulation to make the rating match the absolute skill so obtained.

 Come back later, we're
 still working on this one...

Comparing ratings from different eras :

Actual Elo evaluations allow the average of top players to drift substantially over time and the individual ratings are subject to considerable uncertainty.

The skills of individual players throughout history is best estimated by analyzing a significant sample of the individual moves they actually played in the midgame  without  significant time constraints.

The opening moves should not be examined,  as those depend greatly on current fashion and/or collective encyclopedic knowledge which evolves over time.  Bobby Fisher tried to eliminate that by introducing what's now called Chess960,  where the starting position is randomized among 960 possibilities.

One weakness of this approach is that the current  chess engines  outplay the best human players using an artificial style which is a poor predictor of typical human opposition on a move-by-move basis.  Yet,  the results so obtained are equally flawed throughout history and give an objective evaluation of actual skills which strongly correlates with performance in actual matches between humans.

Computerization also allows private estimates of the Elo rating of players who don't participate in regular chess tournaments with FIDE-rated players.

Elo rating system   |   Arpad Elo (1903-1992)   |   Chessmetrics   |   Jeff Sonas
Comparing top chess players in History
 
The Elo Rating System for Chess and Beyond (7:08)  by  James Grime  (Singingbanana, 2019-02-15).


(2018-08-17)   Odds Chess.  Handicapping a single game of chess.
Traditional ways to even out games between players of different strengths.

In a game  at odds of pawn and 2  (P and 2)  the stronger player plays the black pieces without the  f7  pawn and  White  plays two initial moves.

With  rook odds,  White plays without the  a1  rook.  The  "a"  pawn is placed on  a3.

Handicap   |   Odds Chess   |   Odds for Elo Differences


(2018-08-09)   Chess Titles
FIDE titles for over-the-board regular chess play.

Historically,  the title of  Chess Grandmaster  was first formally conferred by  Tsar Nicolas II  upon the five finalists of the  Saint-Petersburg tournament of 1914.  Namely:  José Raúl Capablanca,  Emmanuel Lasker,  Siegbert Tarrasch  Alexandre Alekhine,  and  Frank James Marshall.

When the title was instated by FIDE in 1950,  it was bestowed upon an initial list of  27 outstanding players  still alive.  Complex rules are now in place,  using  tournament norms  and a minimum Elo rating for the award of this top chess distinction and a few lesser titles,  as summarized in the following table:

Elo rating can be achieved anytime before tournament requirements,  if any.
Open  (Either Sex)Women Only
Title  [USCF class]EloTitleElo
Super Grandmaster 2700  
GrandmasterGM2500
International MasterIM2400
  Woman GrandmasterWGM2300
FIDE MasterFM2300  
  Woman International MasterWIM2200
Candidate MasterCM2200  
National MasterNM2200
[ Expert ]2000 Woman FIDE MasterWFM2100
Woman Candidate MasterWCM2000
First Category1 [A]1800 
Advanced2 [B]1600
Intermediate3 [C]1400
Novice4 [D]1200
Class E[E]1000
Class F[F]800
Class G[G]600
Class H[H]450
Class I[I]200
Class J[J]less

Between 1977 and 2003,  FIDE awarded  31  Honorary Grandmaster  titles to chess players with outstanding records,  including  Jonathan Penrose  (brother of  Roger Penrose)  in 1993.  The courtesy couldn't be extended to  Rashid Nezhmetdinov (1912-1974)  who was already dead by then.  Since 2007,  no formal distinction is made between these and other Grandmasters.

The  Grandmaster  distinction was awarded shortly after his death to  Karoly Honfi (1930-1996)  by the FIDE Congress of September 1996,  in Yerevan.

Grandmaster (GM or IGM)   |   List of Grandmasters   |   FIDE titles   |   Chess titles
 
World Chess Federation (FIDE, Fédération Internationale des Echecs)   |   European Chess Union (ECU)
USCF   |   DSB   |   FFE   |   FSI   |   FEDA   |   KNSB   |   PZSzach
ECF   |   Chess Scotland   |   Welsh Chess Union   |   Irish Chess Union


(2018-09-09)   Some Major Chess Clubs and Famous Chess Venues
Including global chess sites hosting online play in the Computer Era.

The first chess club was organized in Italy in 1550.  Come back later, we're
 still working on this one...

Some major computer sites hosting, at least, online play and tactical puzzle training:

 Come back later, we're
 still working on this one...

Tigran Petrosian Chess House
  (Carolus Chess,
How St Louis became America's chess capital  (The Economist, 2017-05-02).
Park Royal mall  in  Vancouver, BC:  Chess banned on 2016-04-01 returned 2017-04-25.
 
Chess Park  -  Santa Monica, California (0:54)  by  Gina Guddat  (2011-06-25).
Jedi Knight Brian vs. Old Russian Master at Plummer Park (11:07)  Coffee Chess  (2017-05-30).


(2022-01-20)   Online Chess Venues
A few major chess sites host many games among its members.

Examples of some of the features they offer:

Chess.com

Lichess

Lichess.org

Chess Tempo  (since 2007)


(2018-08-09)   Leading Chess Players throughout History
Before and after formal World Championships were organized.

Centuries of Chess (38:49)  by  Levy Rozman  (Gothamchess).

In the Renaissance,  the leading chess players listed below were rarely challenged over-the-board in anything resembling a modern tournament.  The reputation of a chess player was often based on the success of the books he wrote.  The list below starts with  Vicent,  who is credited for inventing modern chess,  by increasing the power of the bishop and the queen  (replacing the lowly  fierca  of  shatranj).  The earliest game of modern chess ever recorded, in the form of a poem,  was  Scachs d'amor (1475)  at a time when castling and  en passant  capture were probably not yet standard.  The first treatise was written by Vicent in 1493.

Last column indicates main residence during peak years.
PeriodPurported Strongest PlayerAliveHome
1495Francesc Vicent 1450-c.1512Salamanca
c. 1497Luis Ramírez de Lucena 1465-1530Salamanca
1512Pedro Damiano 1480-1544Rome
1549-1559Paolo Boiil Bove, the Syracusian 1528-1598Naples
1559-1575Ruy López de Segura c.1530-c.1580Salamanca
(1575)Scovara Salamanca?
(1583)Alfonso Ceron 1535-1600 Salamanca?
1575-1597Giovanni Leonardo di Bona (da Cutri) 1542-1597Naples
1597-1620Alessandro Salvio c.1570-c.1640Naples
1620-1634Gioachino Grecoil Calabrese c.1600-c.1634Naples

For a whole century after the death of Greco,  The Calabrese  (Le Calabrais)  the historical record doesn't single out any dominant player,  with the possible exception of Salvio from 1634 to 1640 who may have regained the crown he had held before Greco.  Meanwhile,  the nevralgic center of World-class chess migrated from Naples to Paris...

Diderot  and  Rousseau  reported  that the the undisputed World center of chess in the mid-eighteenth century was the  Café de la Régence  in Paris.  Around 1730,  François Antoine de Légal,  sire de Kermeur  emerged as the most respected player there.  (He spelled his own name  Legall.)

Legall's only extant recorded game is the fabulous 7-move checkmate below,  known far and wide as  Legall's mate.
 
Legall played this in 1750,  against  Saint-Brié  (Black)  at  rook odds  (no rook on a1;  a-pawn moved to a3).
1. e4     e5
2. Bc4    d6
3. Nf3    Bg4
4. Nc3    g6
5. Nxe5   Bxd1 ??
6. Bxf7+  Ke7
7. Nd5#
   Legall's mate

Légal mentored the young Philidor who dethroned him in 1755 and famously held on to the crown for 40 years, till his own death in 1795.  Philidor left Paris during the French Revolution and took on residence at  Parsloe's Coffee House  on St.  James Street  (that chess club was active from 1772 to 1825).  He was soon joined there by Verdoni,  the strongest player in Europe after Philidor  (according to Philidor himself).  Arguably, Verdoni was the strongest chess player in the World between Philidor's death (1795) and his own (1804).

Verdoni had learned chess at a mature age but was clearly superior to the other three leading players he left behind in Paris  (Bernard,  Carlier,  Léger).  Verdoni died in London on 25 January 1804  (in his Panton Street apartment).  His first name and date-of-birth are unknown.  He left his position as  Professor of Chess  in Parsloe's club to his star student  Jacob Henry Sarratt (1772-1819).

The  London Chess Club  was organized on the 6th of April 1807.  Chronologically,  it was the third club created in London  (after Slaughter's in 1715 and Parsloe's in 1772).  None of those had yet gained enough momentum to compete with the  Café de la Régence.  So,  after the passing of Philidor and Verdoni,  the crown went back to France.  The three leading players between 1804 and the arrival of Deschapelles (1815) were Bernard,  Carlier  and  Léger  (in no particular order).

Tabulated below are the successive purported modern World champions rooted in that era,  with a few challengers of note  (shaded rows).

Last column indicates main residence during championship years.
PeriodAgeNameAliveHome
1730-175528-53Légal de Kermeur1702-1792 Paris
(1737)Philipp Stammac.1705-c.1755 Aleppo/London
(1747)Sir  Abraham Janssen1720-1775 London
1755-179529-69André Danican Philidor 1726-1795Paris / London
1795-1804 Verdoni 17??-1804London
1804-1815Bernard / Carlier / Léger  Paris
1809-181515-21Alexandre Petrov1794-1867 Russia
1815-182135-41Alexandre Deschapelles1780-1847 Paris
1821-184026-45Louis de La Bourdonnais1795-1840 Paris
(1834)(36)Alexander McDonnell1798-1835 London
1840-184340-43Pierre Saint-Amant1800-1872 Paris
1843-185133-41Howard Staunton1810-1874 London
(1846)(27)Tassilo von der Lasa1818-1899 Prussia
1851-1858
1862-1866
33-40
44-48
Adolf Anderssen1818-1879 Breslau
1858-186221-25Paul Morphy1837-1884 New Orleans
(1860)(33)Ignatz Kolisch1837-1889  
(1862)Louis Paulsen1833-1891  
1866-1886
1886-1894
30-58Wilhelm Steinitz1836-1900 London / NYC
1878-1886 Johannes Zukertort1842-1888 London
(1892)(42)Mikhail Chigorin1850-1910Russia
(1892)(30)Siegbert Tarrasch1862-1934 Munich
1894-192126-52 Emanuel Lasker (Theorem)1868-1941Germany
(1895)(22) Harry Nelson Pillsbury1872-1906US
(1910)(35) Carl Schlechter1874-1918Vienna
(1913)(36)Frank Marshall1877-1944US
(1914)(33)Akiba Rubinstein1880-1961Poland
1921-192733-39José Raúl Capablanca1888-1942 Cuba
1927-1935
1937-1946
35-43
45-53
Alexander Alekhine1892-1946 Russia
France
(1929)(43)Aron Nimzovitch1886-1935 Copenhagen
1935-193734-36Max Euwe1901-1981 Netherlands
Salo Flohr1908-1983 Prague
(1938)Paul Keres1916-1975Estonia
(1938)Reuben Fine1914-1993New-York
1948-1957
1958-1960
1961-1963
37-46
47-49
50-52
Mikhail Botvinnik 1911-1995Leningrad
(1951)(27) David Bronstein1924-2006Moscow
1957-195836Vasily Smyslov1921-2010Russia
1960-196124Mikhail Tal1936-1992 Riga
1963-196934-40Tigran Petrosian1929-1984 Moscow
1969-197232-35Boris Spassky1937- Leningrad
1972-197529-32Bobby Fischer1943-2008 Brooklyn
1975-1985
1993-1999
Anatoly Karpov1951-Russia
(1978)(47) Viktor Korchnoi1931-2016Switzerland
1985-1993
1993-2000
Garry Kasparov
né Garik Kimovich Weinstein
1963- Russia
(1993)(28) Nigel Short1965-UK
1999-2000Alexander Khalifman1966-Russia
2000-2006
2006-2007
Vladimir Kramnik 1975-Russia
2000-2002
2007-2013
Vishy Anand1969-India
2002-2004Ruslan Ponomariov1983-Ukraine
2004-2005Rustam Kasimdzhanov1979-Uzbekistan
2005-2006Vesselin Topalov1975-Bulgaria
(2007)Vassily Ivanchuk1969-Ukraine
2013-202322-32Magnus Carlsen1990-Norway
(2014)(32) Levon Aronian1982-Armenia/US
(2018)(26) Fabiano Caruana1992-US / Italy
2023-now31-Ding Liren1992-China

In the above table,  yellow highlighting  is for the 17 people who have been  undisputed  World champions at some point after the  Steinitz era.  Two of them  (Kasparov and Kramnik)  held the  PCA/Braingames title at the dates indicated in red during the period  (1993-2006)  when that title what distinct from the FIDE title.  Dates in black correspond to the World title recognized by FIDE.  The two titles were reunited in 2006 when Kramnik held them both.  He was then heralded as the  14th  modern  World Chess Champion.

World Chess Championship (WCC)   |   PCA (1993-1996)
World Senior Chess Championship (since 1991)   |   World_Rapid Chess Championship
Traité des Amateurs (Paris, 1775)
Deschapelles, the Pumpkin Farmer  by  Sarah Beth   (Chess.com, 2008-07-20)
Parsloe's in 1795, by Murray (1907)  by  Sarah Beth   (Chess.com, 2013-09-10)
Almost a Champion  by  Sarah Beth   (Chess.com, 2015-07-22)
Chess Masters  (Geni.com)
 
Les champions de l'Histoire: Stamma (50:27)  by  Vincent Di Martino  (2012-01-14).
 
Greatest chess-players of the 16th century  (chess.com).
 
43% of the time, the World Champion isn't rated best  by  Nathaniel Green  (chess.com).
 
Animation:  The top chess players over time (6:08)  by  Abacaba  (2016-04-03).
 
Animation:  Top Money Earnerd in Chess History (2:45)  by  Abacaba  (2016-04-03).
 
History Of Chess: The World Chess Championship (1:14:37)  by  Chess.com  (2022-08-21).


(2020-05-16)   Greatest Chess Moves of All Time
Some of the most brilliant moces ever played.

Greatest Chess Move Of All Time, by Frank Marshall (7:03)  GM Simon Williams  (2019-10-09).
 
Great Move by Alexey Shirov (13:21)  by  Antonio Radic  (Agadmator, 2017-12-13).

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 still working on this one...

Chess Jargon
Common chess terms,  classified by topic.

This is a work in progress...

  • Woodpusher :  Clueless chess player.
  • Flag an opponent :  Win on time  (old clocks raised a flag on timeout).

Types of Moves :

  • Waiting move :  A neutral move played to get out of  zugzwang.
  • Safing a piece :  Moving an attacked piece to a  safe square.
  • Pawn Push : 
  • Rook Lift : 
  • Fianchetto : 
  • Zwischenzug (ZZ) :  Intermezzo.  Intermediate strike.  Delaying an obvious opportunity to carry on an unrelated one (usually starting with a check).
  • Sac :  Sacrifice.  Abbreviated noun or verb  (sacced  preferred to  sacked).
  • Desperado :  Sacrificing a doomed piece in the most advantageous way.

Tactical Situations :

  • Hanging :  (en prise).  Said of an insufficiently protected piece.
  • Attacker :.
  • Defender :.
  • X-ray defense :.
  • Fork :  (fourchette).  Piece directly attacking several pieces.
  • Royal Fork (or family fork) :  Knight forking the opposing king and queen.
  • Pin :  (clouage).
  • Skewer :  (enfilade, brochette).
  • Tine :  Rarely used term for a  triple-fork.
  • Passive sacrifice :  Allowing a capture to attend some other business.
  • Coercion :  Pushing a piece into a location  (by threats, not sacrifices).
  • Attraction :  Pulling a piece into a square by offering a sacrifice at there.
  • Deflection or Distraction :  (déviation).  Forcing a piece away from a duty  (especially as defender of another piece).
  • Hook & Ladder trick :  Snatch queen with a back-rank rook sacrifice.
  • (In) zugzwang :  Situation when the obligation to play next is a liability.
  • Perp :  Perpetual check,  would cause a draw  (repetition or 50-move).

Strategical Situations :

  • Compensation :  Stategical gain obtained from a tactical loss.

Types of Mates :

  • Pure Mate :  The mating side attacks once and only once what's needed next to the king  (vacant squares, king and its enemies).  Not king's friends.
  • Smothered Mate :  (mat à l'étouffée)  King only blocked by friendly pieces.
  • Suffocation mate :  (mat à l'étouffée)  King mostly blocked by friends.
  • Corridor Mate :  (mat du couloir).

Glossary of Chess

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