The starting position for Chess960 must meet certain rules. White pawns are placed on the second rank as in regular chess. All remaining white pieces are placed randomly on the first rank, but with the following restrictions:
The black pieces are placed equal-and-opposite to the white pieces. For example, if the white king is placed on f1, then the black king is placed on f8. Note that the king never starts on file a or h, because there would be no room for a rook. The starting position can be generated before the game either by a computer program or using dice, coin, cards, etc.
This procedure generates any of the 960 possible initial positions with an equal chance; on average, this particular procedure uses 6.7 die rolls. Note that one of these initial positions is the standard chess position, at which point a standard chess game begins.
It is also possible to use this procedure to see why there are exactly 960 possible initial positions. Each bishop can take one of four positions, the queen one of six, and the two knights can have five or four possible positions, respectively. (That leaves three open squares and the king must occupy the middle of those three squares, with rooks taking the last two squares, with no choice.) This means that there are 4×4×6×5×4 = 1920 possible positions if the two knights were different in some way. However, the two knights are indistinguishable during play; if they were swapped, there would be no difference. This means that the number of distinguishable positions is half of 1920, or 1920/2 = 960 possible distinguishable positions.
After castling, the rook and king's final positions are exactly the same positions as they would be in standard chess. Thus, after a-side castling (also called sometimes c-castling) the king is on c-file (c1 for White and c8 for Black) and the a-side Rook is on d-file (d1 for White and d8 for Black). This castling notated as O-O-O and known as queen-side castling in orthodox chess. After h-side castling (also called sometimes g-castling) the King is on g-file and the h-side Rook is on f-file. This move notated as O-O and known as king-side castling in orthodox chess. It is recommended that a player state "I am about to castle" before castling, to eliminate potential misunderstanding.
However, castling may only occur under the following conditions. The first two are identical to the standard chess castling rules. The third is an extension of the standard chess rule, which requires only that the squares between the king and castling rook must be vacant.
If the initial position happens to be the standard chess initial position, these castling rules have exactly the same effect as the standard chess castling rules. In some starting positions, some squares can stay filled during castling that would have to be vacant in standard chess. For example, after a-side castling (O-O-O), it's possible to have a, b, and/or e still filled, and after h-side castling (O-O), it's possible to have e and/or h filled. In some starting positions, the king or rook (but not both) do not move during castling.
Eric van Reem suggests other ways to castle:
In the meantime there has been an adjustment setting of the WNCA that when performing a castling move it is irrelevant in which sequence involved pieces were touched. All pieces involved in a move may be touched arbitrarily. When castling those pieces are the King and Rook, and in capturing moves they are the capturing and the captured piece. Especially with players new to Chess960 it might make sense also to announce a castling to avoid misunderstandings. When a chess clock will be used, pressing the button could be taken as a sign that a castling move has been completed.
When castling using a computer interface, programs should have separate a-side (O-O-O) and h-side (O-O) castling actions (e.g., as a button or menu item). Ideally, programs should also be able to detect a king or rook move that cannot be anything other than a castling move and consider that a castling move. Recommended gestures are: the King is moving to his at least two steps distant castling target square or else upon the involved Rook, to avoid by this a possible confusion with normal King's moves.
When using an electronic board, to castle one should remove the king, remove the castling rook, place the castling rook on its new position, and then place the king on its new position. This will create an unambiguous move for electronic boards, which often only have sensors that can detect the presence or absence of an object on each square (and cannot tell what object is on the square). Ideally, electronic boards should detect a king or rook move that can only be a castling move as well, but users should not count on this.
The study of openings for Chess960 is in its infancy, but opening fundamentals still apply. These include: protect the King, control the center squares (directly or indirectly), and develop your pieces rapidly starting with the less valuable pieces. Some starting positions have unprotected pawns that may need to be dealt with quickly.
Some have argued that two games should be played with each initial position, with players alternating as white and black, since some initial positions may turn out to give white a much bigger advantage than standard chess. However, there is no evidence that any position gives either side a significant advantage greater than the advantage white already has in orthodox chess.
Since the initial position is usually not the orthodox chess initial position, recorded games must also record the initial position. Games recorded using the Portable Game Notation (PGN) can record the initial position using Forsyth-Edwards Notation (FEN), as the value of the "FEN" tag. Castling is marked as O-O or O-O-O, just as in standard chess. Note that not all chess programs can handle castling correctly in Chess960 games (except if the initial position is the standard chess initial position). To correctly record a Chess960 game in PGN, an additional "Variant" tag must be used to identify the rules; the rule named "Fischerandom" is accepted by many chess programs as identifying Chess960, though "Chess960" should be accepted as well. Be careful to use "Variant" and not "Variation", which has a different meaning. This means that in a PGN-recorded game, one of the PGN tags (after the initial 7 tags) would look like this: [Variant "Fischerandom"].
FEN is capable of expressing all possible starting positions of Chess960. However, unmodified FEN cannot express all possible positions of a Chess960 game. In a game, a rook may move into the back row on the same side of the king as the other rook, or pawn(s) may be underpromoted into rook(s) and moved into the back row. If a rook is unmoved and can still castle, yet there is more than one rook on that side, FEN notation as traditionally interpreted is ambiguous. This is because FEN records that castling is possible on that side, but not which rook is still allowed to castle.
A modification of FEN, X-FEN, has been devised by Reinhard Scharnagl to remove this ambiguity. In X-FEN, the castling markings "KQkq" have their expected meanings: "Q" and "q" mean a-side castling is still legal (for white and black respectively), and "K" and "k" mean h-side castling is still legal (for white and black respectively). However, if there is more than one rook on the baseline on the same side of the king, and the rook that can castle is not the outermost rook on that side, then the file letter (uppercase for white) of the rook that can castle is used instead of "K", "k", "Q", or "q"; in X-FEN notation, castling potentials belong to the outermost rooks by default. The maximum length of the castling value is still four characters. X-FEN is upwardly compatible with FEN, that is, a program supporting X-FEN will automatically use the normal FEN codes for a traditional chess starting position without requiring any special programming. As a benefit all 18 pseudo FRC positions (positions with traditional placements of rooks and king) still remain uniquely encoded.
The solution implemented by chess engines like Shredder and Fritz is to use the letters of the columns on which the rooks began the game. This scheme is sometimes called Shredder-FEN. For the traditional setup, Shredder-FEN would use HAha instead of KQkq.
In 2001, Lékó became the first Fischer Random Chess world champion, defeating GM Michael Adams in an eight game match played as part of the Mainz Chess Classic. There were no qualifying matches (also true of the first orthodox world chess champion titleholders), but both players were in the top five in the January 2001 world rankings for orthodox chess. Lékó was chosen because of the many novelties he has introduced to known chess theories, as well as his previous tournament win; in addition, Lékó has played Chess960 games with Fischer himself. Adams was chosen because he was the world number one in blitz (rapid) chess and is regarded as an extremely strong player in unfamiliar positions. The match was won by a narrow margin, 4½ to 3½.
In 2002 at Mainz, an open tournament was held which attracted 131 players. Peter Svidler won the event. Other interesting events happened in 2002. The website ChessVariants.org selected Fischer Random chess as its "Recognized Variant of the Month" for April 2002. Yugoslavian Grandmaster Svetozar Gligoric published in 2002 the book Shall We Play Fischerandom Chess?, popularizing this variant further.
At the 2003 Mainz Chess Classic, Svidler beat Lékó in an eight game match for the World Championship title by a score of 4.5 - 3.5. The Chess960 (Fischer Random Chess) open tournament attracted 179 players, including 50 GMs. It was won by Levon Aronian (Armenia), the 2002 World Junior Champion.
Aronian played Svidler for the title at the 2004 Mainz Chess Classic, losing 4.5-3.5. At the same tournament in 2004, Aronian played two Chess960 games against the Dutch computer chess program The Baron, developed by Richard Pijl. Both games ended in a draw. It was the first ever man against machine match in Chess960. Zoltán Almási won the Chess960 open tournament in 2004.
In 2005, The Baron played two Chess960 games against Chess960 World Champion Peter Svidler; Svidler won 1.5-0.5. The chess program Shredder, developed by Stefan Meyer-Kahlen from Düsseldorf, Germany, played two games against Zoltán Almási from Hungary; Shredder won 2-0. Almási and Svidler played an eight-game match at the 2005 Mainz Chess Classic. Once again, Svidler defended his title, winning 5-3. Levon Aronian won the Chess960 open tournament in 2005. During the Chess Classic 2005 in Mainz, initiated by Mark Vogelgesang and Eric van Reem, the first-ever Chess960 computer chess world championship was played. Nineteen programs, including the powerful Shredder, played in this tournament. As a result of this tournament, Spike became the first Chess960 computer world champion.
The 2006 Mainz Chess Classic saw Svidler defending his championship in a rematch against Levon Aronian. This time, Aronian won the match 5-3 to become the third ever Chess960 World Champion. Étienne Bacrot won the Chess960 open tournament, earning him a title match against Aronian in 2007. In 2006 Shredder won the computer championship, making it Chess960 computer world champion. Three new Chess960 world championship matches were held, in the women, junior and senior categories. In the women category, Alexandra Kosteniuk became the first Chess960 Women World Champion by beating Elisabeth Paehtz 5.5 to 2.5. The 2006 Senior Chess960 World Champion was Vlastimil Hort, and the 2006 Junior Chess960 World Champion was Pentala Harikrishna.
In 2007 Mainz Chess Classic Aronian successfully defended his title of Chess960 World Champion over Viswanathan Anand, while Victor Bologan won the Chess960 open tournament. Rybka won the 2007 computer championship.
|Year||World Rapid Championship||Mainz Open||World Rapid Women's Championship||Computer Championship|
|2001||Péter Lékó (4.5-3.5 vs Michael Adams)||-||-||-|
|2003||Peter Svidler (4.5-3.5 vs Péter Lékó)||Levon Aronian||-||-|
|2004||Peter Svidler (4.5-3.5 vs Levon Aronian)||Zoltán Almási||-||-|
|2005||Peter Svidler (5-3 vs Zoltán Almási)||Levon Aronian||-||Spike|
|2006||Levon Aronian (5-3 vs Peter Svidler)||Etienne Bacrot||Alexandra Kosteniuk (5.5-2.5 vs Elisabeth Pähtz)||Shredder|
|2007||Levon Aronian (2-2, 1.5-0.5 vs Viswanathan Anand)||Victor Bologan||-||Rybka|
|2008||-||Hikaru Nakamura||Alexandra Kosteniuk (2.5-1.5 vs Kateryna Lahno)||Rybka|
This particular chess variant has a number of different names. The original name is Shuffle Chess. After Bobby Fischer formalised his variation of Shuffle Chess, the names applied to it included "Fischer Random Chess" and "Fischerandom Chess". However, as it became more popular many objected to this name. Some object to having the name of any person attached to the game; others object because they object to many of Mr. Fischer's actions over the years. Others felt that the minor modifications made by Fischer did not entitle him to change the name of the variant.
Hans-Walter Schmitt (chairman of the Frankfurt Chess Tigers e. V.) is an advocate of this chess variant, and he started a brainstorming process to choose a new name for it. The new name had to obey the following requirements on the parts of some leading grandmasters:
This effort culminated in the name "Chess960," deriving from the number of different initial positions.
R. Scharnagl, another proponent of this variant, had used the term FullChess instead. But today he uses "FullChess" to address chess variants consistently embedding the traditional chess game, e.g. Chess960 and some new variants based on the extended 10x8 Capablanca piece set Capablanca chess. He currently recommends the use of the term "Chess960" instead of Fischer Random Chess for this particular set of rules.
Bobby Fischer never stated in public whether he accepted the name 'Chess960'.
Edward Northam suggests the following approach for allowing players to jointly create a position without randomizing tools: First, the back ranks are cleared of pieces, and the white Bishops, Knights, and Queen are gathered together. Starting with Black, the players, in turn, place one of these pieces on White's back rank, where it must stay. The only restriction is that the Bishops must go on opposite colored squares. There will be a vacant square of the required color for the second Bishop, no matter where the previous pieces have been placed. Some variety could be introduced into this process by allowing each player to exercise a one time option of moving a piece already on the board instead of putting a new piece on the board. After all five pieces have been put on the board, the King must be placed on the middle of the three vacant back rank squares that remain. Rooks go on the other two.
This approach to the opening setup has much in common with Pre-Chess, the variant in which White and Black, alternately and independently, fill in their respective back ranks. Pre-Chess could be played with the additional requirement of ending up with a legal Chess960 opening position. A chess clock could even be used during this phase as well as during normal play.
Without some limitation on which pieces go on the board first, it is possible to reach impasse positions, which cannot be completed to legal Chess960 starting positions. Example: Q.RB.N.N If the players want to work with all eight pieces, they must have a prior agreement about how to correct illegal opening positions that may arise. If the Bishops end up on same color squares, a simple action, such as moving the a-side Bishop one square toward the h-file, might be agreeable, since there is no question of preserving randomness. Once the Bishops are on opposite colored squares, if the King is not between the Rooks, it should trade places with the nearest Rook.
Note also that although the game can start with any of 960 starting positions, half of these are actually mirror positions that theoretically don't change the games' tactics.
Naturally, the right to castle is lost:
And castling is prevented temporarily:
Note: There are other claims to the nomenclature 'Chess480'. Reinhard Scharnagl defines it as the white queen is always to the left of the white king. Another way of defining Chess480 is that the white king must always be located on a dark square. The definition could also be that the white king must always be on a light square. The point is that half the positions are mirror image reversals of the other half. It is really up to the individual to decide how to filter the 480 positions.