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Chess960

Chess960
One of 960 possible starting setups.
Black's setup always mirrors White's.
Years active Since June 19, 1996
Genre(s) Board game
Chess variant
Players 2
Playing time Casual games: usually 10-60 mins.
Tournament games: from 10 mins. (fast chess) to 6+ hrs.
Random chance None
Skill(s) required Strategy, tactics
Synonym(s) Fischer Random Chess
Fischerandom Chess
FR Chess, FRC
New Chess

Chess960 (or Fischer Random Chess) is a variant of chess invented and advocated by former World Chess Champion Bobby Fischer, publicly announced on June 19, 1996 in Buenos Aires, Argentina. It employs the same board and pieces as standard chess; however, the starting position of the pieces on the players' home ranks is randomized. The random setup renders the prospect of obtaining an advantage through the memorization of opening lines impracticable, compelling players to rely on their talent and creativity.

Randomizing the main pieces had long been known as Shuffle Chess; however, Chess960 introduces restrictions on the randomization, "preserving the dynamic nature of the game by retaining bishops of opposite colours for each player and the right to castle for both sides". The result is 960 unique possible starting positions, from which the name "Chess960" is derived.

In 2008 FIDE added Chess960 to an appendix of the rules of chess.

Setup

Before the game, a starting position is randomly determined and set up, subject to certain requirements. After setup, the game is played the same as standard chess in all respects, with the single exception of castling from the different possible starting positions for king and rooks.

Starting position requirements

White pawns are placed on the second rank as in standard chess. All remaining white pieces are placed randomly on the first rank, with two restrictions:

  1. The bishops must be placed on opposite-color squares.
  2. The king must be placed on a square between the rooks.

Black's pieces are placed equal-and-opposite to White's pieces. For example, if the white king is randomly determined to start on f1, then the black king is placed on f8. (The king never starts on the a - or h -file, since this would leave no space for a rook.)

Determining a starting position

The special arrangement of pieces on the players' first ranks is selected randomly before play according to Chess960 rules, and can be generated either by a computer program, or using dice, coin, cards, etc. Regardless of which method is used, there should be an equal probability for each of the 960 possible starting positions to occur.

Why 960?

Each bishop can take one of four positions, the queen one of six, and the two knights can assume five or four possible positions respectively. This leaves three open squares which the king and rooks must occupy according to setup stipulations, without choice. This means there are 4x4x6x5x4 = 1920 possible starting positions if the two knights were different in some way. However, the two knights are indistinguishable during play (if swapped, there would be no difference), so the number of distinguishable possible positions is half of 1920, or 1920/2 = 960. (Half of the 960 are left-right mirror images of the other half, however Chess960 castling rules preserve left-right asymmetry in play.)

Castling rules

In Chess960, each player may castle once per game, the same as standard chess, moving both the king and a rook in a single move; however, the castling rules were reinterpreted in Chess960 to support the different possible initial positions of the king and rook. After castling, the king and rook final positions are exactly the same as they are in standard chess. Thus:

Examples of castling
a b c d e f g h
8
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
An initial position of kings and rooks
a b c d e f g h
8
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
Black has castled h-side (0-0) and White has castled a-side (0-0-0).

Castling in Chess960 has the same prerequisites as castling under standard chess rules, namely:

A recommended way to castle is to move the king outside the playing area next to its final position, then the rook from its starting to ending square, then lastly to place the king on its final square. This technique is always unambiguous and simple to perform. It is also useful for player to state "I am about to castle" before castling, to avoid potential misinterpretation.

Observations

In some starting positions, some squares can remain occupied during castling that would have to be vacant in standard chess. After a-side castling (0-0-0), it is possible that a, b, and/or e are still filled; and after h-side castling (0-0), it is possible that e and/or h are filled. In some starting positions, the king or rook (but not both) do not move during castling.

Theory

a b c d e f g h
8
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
In this start position, the players' a- and b-pawns are unguarded and subject to immediate attack if either player moves their f- or g-pawns.

The study of openings in Chess960 is in its infancy, but fundamental opening principles still apply, including: protect the king, control the central squares (directly or indirectly), and develop rapidly, starting with the less valuable pieces. Unprotected pawns may also need to be dealt with quickly. The majority of starting positions have unprotected pawns, and some starting positions have up to two unprotected pawns that can be attacked on the first move (see example diagram).

It has been argued that two games should be played from each starting position, with players alternating as White and Black, since some initial positions may offer White a bigger advantage than in standard chess. For example, in some Chess960 starting positions White can attack an unprotected black pawn after the first move, whereas in standard chess it takes two turns for White to attack and there are no unprotected pawns. (See First-move advantage in chess.)

History

Chess960 is a variant of Shuffle Chess, which had been suggested as early as 1792 with games played as early as 1842. Fischer's modification "imposes certain restrictions, arguably an improvement on the anarchy of the fully randomized game in which one player is almost certain to start at an advantage". Fischer started work on his new version of chess after the 1992 return match with Boris Spassky. The result was the formulation of the rules of Fischerandom Chess in September 1993, introduced formally to the chess public on June 19, 1996 in Buenos Aires, Argentina.

Fischer's goal was to eliminate what he considered the complete dominance of openings preparation in chess today, replacing 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 to fix every move of the game. Since the "opening book" for 960 possible opening systems would be too difficult to devote to memory, the players must create every move originally. From the first move, both players must devise original strategies and cannot use well-established patterns. Fischer believed that eliminating memorized book moves would level the playing field.

Tournaments

1996. The first Fischerandom Chess tournament was held in Vojvodina, Yugoslavia in the spring of 1996, and was won by GM Péter Lékó with 9½/11, ahead of GM Stanimir Nikolić with 9 points.

2010. In 2010 the US Chess Federation sponsored its first Chess960 tournament, at the Jerry Hanken Memorial US Open tournament in Irvine, California. This one-day event, directed by Damian Nash, saw a first place tie between GM Larry Kaufman and FM Mark Duckworth.

2012. The British Chess960 Championship was held at the Mind Sports Olympiad, and won by Ankush Khandelwal.

Mainz Championships

Note: All of these championships are unofficial, in that they are not recognized by FIDE. Furthermore, they are all played at rapid time controls.

2001. 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 standard chess world chess champion titleholders), but both players were in the top five in the January 2001 world rankings for standard 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 supposedly played Fischer Random Chess 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.

2002. In 2002 at Mainz, an open tournament was held which was attended by 131 players, with Peter Svidler taking first place. Fischer Random Chess was selected as the April 2002 "Recognized Variant of the Month" by The Chess Variant Pages (ChessVariants.org). The book Shall We Play Fischerandom Chess? was published in 2002, authored by Yugoslavian grandmaster Svetozar Gligorić.

2003. At the 2003 Mainz Chess Classic, Svidler beat Lékó in an eight-game match for the World Championship title by a score of 4½-3½. The Chess960 open tournament drew 179 players, including 50 GMs. It was won by Levon Aronian, the 2002 World Junior Champion. Svidler is the official first World New Chess Association (WNCA) world champion inaugurated on August 14, 2003 with Jens Beutel, Mayor of Mainz as the President and Hans-Walter Schmitt, Chess Classic organiser as Secretary. The WNCA maintains an own dedicated Chess960 rating list.

2004. Aronian played Svidler for the title at the 2004 Mainz Chess Classic, losing 4½-3½. 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.

2005. 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.

2006. 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 Fischer Random Chess 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 Pähtz 5½ to 2½. The 2006 Senior Chess960 World Champion was Vlastimil Hort, and the 2006 Junior Chess960 World Champion was Pentala Harikrishna.

2007. 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.

2008. Hikaru Nakamura won the 2008 Finet Chess960 Open (Mainz).

2009. The last Mainz tournament was held in 2009.

Computers

5th Livingston Chess960 Computer World Championship 2009 at Mainz. The four programs Deep Sjeng, Shredder, Rybka and Ikarus (with the programmers).

In 2005, chess program The Baron played two Chess960 games against Chess960 World Champion Peter Svidler; Svidler won 1½-½. The chess program Shredder, developed by Stefan Meyer-Kahlen of Germany, played two games against Zoltán Almási from Hungary; Shredder won 2-0.

Summary of Mainz Winners

Year Chess960 Championship Open Chess960 Women's Championship Computer Chess960 Championship
2001 Péter Lékó (4½-3½ vs Michael Adams)
2002 Peter Svidler
2003 Peter Svidler (4½-3½ vs Péter Lékó) Levon Aronian
2004 Peter Svidler (4½-3½ vs Levon Aronian) Zoltán Almási
2005 Peter Svidler (5-3 vs Zoltán Almási) Levon Aronian Spike
2006 Levon Aronian (5-3 vs Peter Svidler) Étienne Bacrot Alexandra Kosteniuk (5½-2½ vs Elisabeth Pähtz) Shredder
2007 Levon Aronian (2-2, 1½-½ vs Viswanathan Anand) Victor Bologan Rybka
2008 Hikaru Nakamura Alexandra Kosteniuk (2½-1½ vs Kateryna Lahno) Rybka
2009 Hikaru Nakamura (3½-½ vs Levon Aronian) Alexander Grischuk Rybka

 

Naming

Hans-Walter Schmitt, Frankfurt 2011

The variant has held a number of different names. It was initially known as "Fischerandom Chess" after Fischer formalized his variation of Shuffle Chess. Later name forms included "Fischer Random Chess", "FR Chess", and "FRC".

Hans-Walter Schmitt, chairman of the Frankfurt Chess Tigers e.V. and an advocate of the variant, started a brainstorming process for selecting a new name, which had to meet requirements of leading grandmasters; specifically, the new name and its parts:

The effort culminated in the name choice "Chess960" - derived from the number of different possible starting positions.

R. Scharnagl, another proponent of the variant, advocated the term "FullChess". However today he uses FullChess to refer to variants which consistently embed standard chess (e.g. Chess960, and some new variants based on the extended 10x8 piece set in Capablanca chess). He currently recommends the name Chess960 in preference to Fischer Random Chess for the variant.

Bobby Fischer never publicly stated his feeling about the name "Chess960".

Quotes

Lékó-Adams, Mainz 2001
a b c d e f g h
8
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
Game 4

Coding games and positions

Recorded games must convey the Chess960 starting 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 notated the same as in standard chess (except PGN requires letter O not number 0). Note that not all chess programs can handle castling correctly in Chess960 games. To correctly record a Chess960 game in PGN, an additional "Variant" tag (not "Variation" tag, which has a different meaning) 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. This means that in a PGN-recorded game, one of the PGN tags (after the initial seven 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.

Related variants

Non-random setups

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-color 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-color squares, if the king is not between the rooks, it should trade places with the nearest rook.

Chess480

Examples of Chess480 castling
a b c d e f g h
8
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
An initial position of kings and rooks
a b c d e f g h
8
8
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
White has castled h-side (0-0) and Black has castled a-side (0-0-0).

John Kipling Lewis's "Castling in Chess960: An appeal for simplicity" proposes the same rules for the initial position as Chess960, but proposes an alternative set of castling rules which Lewis has named "Orthodoxed Castling". The preconditions for castling are the same as in Chess960, but when castling,

[...] the king is transferred from its original square two squares towards (or over) the rook, then that rook is transferred to the square the king has just crossed (if it is not already there). If the king and rook are adjacent in a corner and the king cannot move two spaces over the rook, then the king and rook exchange squares.

Unlike Chess960, the final position after castling in Chess480 will usually not be the same as the final position of a castling move in traditional chess. Lewis argues that this alternative better conforms to how the castling move was historically developed.

Lewis has named this chess variation "Chess480"; it follows the rules of Chess960 with the exception of the castling rules. 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.

Although a Chess480 game can start with any of 960 starting positions, half of these are actually mirror positions that theoretically don't change the games' tactics. Another way of defining Chess480 is that the white king must always be located on a dark square. Another satisfactory definition is 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.

David O'Shaughnessy argues in "Castling in Chess480: An appeal for sanity" that the Chess480 rules are often not useful from a gameplay perspective. In about 66% of starting positions, players have the options of castling deeper into the wing the king started on, or castling into the center of the board (when the king starts on the b-, c-, f-, or g-files). From Wikipedia article Castling: "Castling is an important goal in the early part of a game, because it serves two valuable purposes: it moves the king into a safer position away from the center of the board, and it moves the rook to a more active position in the center of the board." An example of poor castling options is a position where the kings start on g1 and g8 respectively. There will be no possibility of "opposite-side castling" where each player's pawns are free to be used in pawn storms, as the kings' scope for movement is very restricted (it can only move to the h- or e-file). These "problem positions" play well with Chess960 castling rules.

Others

There are several other variants based on randomization of the initial setup. "Randomized Chess, in one or other of its many reincarnations, continues to attract support even, or perhaps especially, that of top players." (Pritchard 2000:17)

Double Fischer Random Chess
The same as Chess960, except the White and Black starting positions do not mirror each other.

Transcendental chess (or TC)
The same as Double Fischer Random, minus the restriction that the king is between rooks, and there is no castling. The variation Auction TC introduces the concept of auction (offering extra moves for the right of picking the side). By Maxwell Lawrence (1978).

Moab Random Chess
A variant of Shuffle Chess, using the same initial positions as Transcendental chess and Double Fischer Random, except that the setup phase is part of the game. Players take turns placing back-rank pieces on their side or their opponent's. Castling rules are replaced with a one-time "evacuation" of the king to any empty first-rank square.

Shuffle Chess
The parent variant of Chess960. There are no restrictions on the back-rank shuffles, with castling possible only when king and rook are on their traditional starting squares.

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