Fischer random chess, also known as Chess960 ('chess nine-sixty'), is a variation of the game of chess invented by the former world chess champion Bobby Fischer. Fischer announced this variation on June 19, 1996, in Buenos Aires, Argentina. Fischer random chess employs the same board and pieces as classical chess, but the starting position of the pieces on the players' is randomized, following certain rules. The random setup makes gaining an advantage through the memorization of openings impracticable; players instead must rely more on their skill and creativity .
Randomizing the main pieces had long been known as shuffle chess, but Fischer random chess introduces new rules for the initial random setup, "preserving the dynamic nature of the game by retaining for each player and the right to castle for both sides". The result is 960 unique possible starting positions.
In 2008, FIDE added Chess960 to an appendix of the Laws of Chess. The first world championship officially sanctioned by FIDE, the FIDE World Fischer Random Chess Championship 2019, brought additional prominence to the variant. It was won by Wesley So. In 2022, Hikaru Nakamura became the new champion.
Setup
Before the game, a starting position is randomly determined and set up, subject to certain requirements. White's pieces (not pawns) are placed randomly on the first , following two rules: The bishops must be placed on opposite-color squares. 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.) Pawns are placed on the players' second ranks as in classical chess.
After setup, the game is played the same as classical chess in all respects, with the exception of castling from the different possible starting positions for king and rooks.
Creating starting positions
There are 4 × 4 × 6 × 10 × 1 = 4 × 4 × 15 × 4 × 1 = 960
legal starting positions: 4 light squares for one bishop; 4 dark squares for the other bishop; 6 remaining squares for the queen and 5! / (3! × 2!) = 5 × 4 / 2 = 10 ways to place the two (identical) knights on the remaining 5 squares, or, equivalently, 6! / (4! × 2!) = 5 × 6 / 2 = 15 ways to place the two (identical) knights on the remaining 6 squares and 4 remaining squares for the queen; 1 way to place the two rooks and king on the remaining 3 squares, since the king must be between the rooks.
Usually, the players accept the conditions of the organizer to generate the starting position with software. If the software is not available or the players do not accept it, there are many ways to generate a random starting position with equal probability. This requires choosing a number randomly between 0 and 959 inclusive; this number is then used as an index to the Fischer random chess numbering scheme.
In 1998, Ingo Althöfer proposed a method that requires only a single standard die. (Re-roll if needed to get values in the range 1–4 or 1–5).
960 choices can be obtained in several ways by combining polyhedral dice without re-rolling; for example 4×12×20 or 6×8×20 or 8×10×12.
Shuffling marked objects (cards, pieces, pawns, dominoes, Scrabble letters) and use the permutations. For example, shuffle 14 marked cards a,b,c,d,e,f,g,h, N,N,Q,R,R,R and place them, in this random order, separated into three rows: For the black squares (a,c,e,g); For the white squares (b,d,f,h);
The first card of each row determines one bishop's place.
The remaining cards Q,R,R,R,N,N place the queen, rooks and knights respectively in the remaining squares; the king must be between the rooks, so it takes the middle of the three 'R' squares.
Naming
The variant has held a number of different names. It was originally known as "Fischerandom" or "Fischerandom chess", the name given by Fischer. "Fischer random chess" is the official term, used by FIDE.
Hans-Walter Schmitt, chairman of the Frankfurt Chess Tigers e.V. and an advocate of the variant, started a brainstorming process for creating a new name, which had to meet the requirements of leading grandmasters; specifically, the new name and its parts: should not contain part of the name of any grandmaster; should not include negatively biased or "spongy" elements (such as "random" or "freestyle"); and should be universally understood. The effort culminated in the name choice "Chess960" – derived from the number of different possible starting positions. Fischer never publicly expressed an opinion on the name "Chess960".