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Chess960, also called Fischer Random Chess, is a chess variant produced by Grandmaster Bobby Fischer by modifying the rules of Shuffle Chess so that castling possibilities exist for all starting postions. It was originally announced on June 19, 1996, in Buenos Aires, Argentina. Fischer's goal was to create a chess variant in which chess creativity and talent would be more important than memorization and analysis of opening moves. His approach was to create a randomized initial chess position, which would thus make memorizing chess opening move sequences far less helpful. The initial position is set up in a special way and there are 960 such positions, thus the name 'Chess960'.
Before the game a starting position is randomly set up, subject to certain rules. After this, the game is played in the same way as standard chess. In particular, pieces and pawns have their normal moves, and each player's objective is to checkmate the opponent's king.
Starting position requirements
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 king is placed somewhere between the two rooks.
- The bishops are placed on opposite-colored squares.
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.
Determining a starting position
There are many procedures for creating this starting position. A common one is that proposed by Hans L. Bodlaender, which uses one six-sided die to create an initial position. Typically this is done just before the game commences:
- Roll the die, and place a white bishop on the black square indicated by the die, counting from the left. Thus 1 indicates the first black square from the hi left (a1 in algebraic notation), 2 indicates the second black square from the left (c1), 3 indicates the third (e1), and 4 indicates the fourth (g1). Since there are no fifth or sixth positions, re-roll 5 or 6 until another number shows.
- Roll the die, and place a white bishop on the white square indicated (1 indicates b1, 2 indicates d1, and so on). Re-roll 5 or 6.
- Roll the die, and place a queen on the first empty position indicated (always skipping filled positions). Thus, a 1 places the queen on the first (leftmost) empty position, while a 6 places the queen on the sixth (rightmost) empty position.
- Roll the die, and place a knight on the empty position indicated. Re-roll a 6.
- Roll the die, and place a knight on the empty position indicated. Re-roll a 5 or 6.
- This leaves three empty squares. Place a white rook on the first empty square of the first rank, the white king on the second empty square of the first rank, and the remaining white rook on the third empty square of the first rank.
- Place all white and black pawns on their usual squares, and place Black's pieces to exactly mirror White's (so Black should have on a8 exactly the same type of piece that White has on a1, except that bishops would be on opposite colors).
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.
Rules for castling
Chess960 allows each player to castle once per game, moving both the king and a rook in a single move. However, a few interpretations of standard chess games rules are needed for castling, because the standard rules presume initial locations of the rook and king that are often untrue in Chess960 games.
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.
- Unmoved: The king and the castling rook must not have moved before in the game, including castling.
- Unattacked: No square between the king's initial and final squares (including the initial and final squares) may be under attack by any opposing piece.
- Unimpeded: All the squares between the king's initial and final squares (including the final square), and all of the squares between the rook's initial and final squares (including the final square), must be vacant except for the king and castling rook. An equivalent way of stating this is that the smallest back rank interval containing the king, the castling rook, and their destination squares contains no pieces other than the king and castling rook.
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.
How to castle
When castling on a physical board with a human player, it is recommended that the king be moved outside the playing surface next to his final position, the rook then be moved from its starting to ending position, and then the king be placed on his final square. This is always unambiguous, and is a simple rule to follow.
Eric van Reem suggests other ways to castle:
- If only the rook needs to move (jumping over the king), you can simply move only the rook.
- If only the king needs to move (jumping over the castling rook), you can simply move the king.
- One can pick up both the king and rook (in either order), then place them on their final squares (this is called "transposition" castling).
- One can move the king to its final square and move the rook to its final square as two separate moves in either order (this is called "double-move" castling). Obviously, if the rook is on the square the king will occupy, the player needs to move the rook first, and if the king is on the square the rook will occupy, the player needs to move the king first.
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.
Examining 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.
Recording games and positions
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"].
Reinhard Scharnagl does not agree. He argues that there is no need for distinguishing the so-called variants "normal", "nocastle" and "fischerandom", because the different or skipped castling rights could be completely encoded in an appropriate FEN string. He believes it would be a bad solution to inflate a PGN file with superfluous tags only to cover weaknesses of some protocols. Instead, he believes that an FRC-aware engine should always be prepared to Chess960. Loaded with a Shuffle Chess FEN string it would play correctly, just like it would handle a traditional chess starting array without error. A game of traditional Chess could easily be recognized via the missing SetUp and FEN tags.
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.
Chess960 is a variant of Shuffle chess defined by former World Champion Bobby Fischer and introduced formally to the chess public on June 19, 1996, in Buenos Aires, Argentina. Shuffle Chess had been played for quite some time before this, as early as 1842. Fischer's goal was to eliminate what he considers the complete dominance of openings preparation in chess today, and to replace it with creativity and talent. His belief about Russians fixing all international games also provided motivation. In a situation where the starting position was random it would be impossible for the Russians to fix every move of the game. Since the opening book for each possible opening position would be too difficult to devote to memory (959 "book opening" systems), therefore, each player must create every move originally. From the first move, both players have to come up with original strategies and can not use well-known thinking patterns. By eliminating memorized book moves, Fischer believes that it will level the playing field; and as an accidental consequence, it makes computer chess programs much weaker, as they depend on the opening book to beat humans .
The first Fischer Random Chess tourney was held in Yugoslavia in the spring of 1996, and was won by Grandmaster Péter Lékó. 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, 4.5 to 3.5.
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, 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.
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 Zoltan Almasi from Hungary; Shredder won 2-0. Almasi and Svidler played an eight-game match at the 2005 Mainz Chess Classic. Once again, Svidler defended his title, winning 5-3.
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 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.
Computer Chess960 world championship
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, became the first Chess960 computer world champion. In 2006 Shredder won the championship, making it Chess960 computer world champion.
This particular chess variant has a number of different names. The first names applied to it include "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. The name Shuffle Chess is no longer used.
(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:
- It should not use parts of the name of any Grandmaster colleague
- It should not include negatively biased or "spongy" elements like "random" or "freestyle"
- It should be understood worldwide.
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 has never stated in public whether he accepts the name 'Chess960'.
Similar chess variants
The initial setup need not necessarily be random. The players or a tournament setting may decide on a specific position in advance, for example. Tournament Directors prefer that all boards in a single round play the same random position, as to maintain order and abbreviate the setup time for each round.
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..NN 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.