It was originally announced on June 19, 1996, in Buenos Aires. 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. The initial position is set up subject to certain rules, resulting in 960 possible initial positions, hence the name 'Chess960'.
Chess960 differs from Chess only inasfar the initial set up of the pieces is concerned. After that, the game is played in the same way as regular Chess. In particular, pieces and pawns have their normal moves, and each player's objective is to checkmate the opponent's king.
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, with the following restrictions:
- The king is placed somewhere between the rooks.
- The bishops are placed on opposite-colored squares.
- The black pieces mirror the white pieces (as in Chess).
Note that the king cannot occupy a cornersquare because there would be no room for a rook. The starting position can be generated before the game by for instance a computer program or dice.
Rules for castling
Chess960 allows each player to castle once per game.
Castling however differs substantially from regular Chess, yet the outcome is forced into a Chess-like configuration, with the king on c1 (c8) and the rook on d1 (d8) in 'C-castling', notated as O-O-O, and the king on g1 (g8) and the rook on f1 (f8) in 'G-castling', notated as O-O.
It is recommended that a player state "I am about to castle" before castling, to eliminate potential misunderstanding.
Castling may only occur under the following conditions.
- The king and the castling rook may not have moved before.
- The king may not be in, move through, or end up in check, that is: no square between the king's initial- and destination-square (inclusive) may be under attack.
- All squares between the king's initial- and destination-square (inclusive), and all squares between the rook's initial- and destination-square (inclusive), must be vacant except for the king and castling rook.
In consequence of these unusual castling rules, in some starting positions, the king or rook (but not both) may not move during castling.
Note: with due reference to "Why do great players make poor inventors?", in the Pit the Chess960 applet has three 'modes', depending on the presence, and if, nature, of castling:
- Mode 1: CG-castling.This is the form of castling Bobby Fischer advocated. It is called CG-castling because the king ends up either on the C-file or on the G-file.
- Mode 2: modified traditional castling.This is the form of castling John Kipling Lewis advocates in the Chess variant pages. Inasfar as castling is logical in a shuffle variant, we consider this an improvement. In his own words: "It seems that simplification of the castling rules for Chess960 could help promote the game for beginners, streamline the rules and reconnect the game with it's historical roots".
- Mode 3: no castling.Castling is justified in Chess because there's a persistent problem concerning rook-development, based on the initial position (concerning the king's safety, the first question that poses itself is: "how safe exactly should a king be in a chess game?"). In Chess960 the problem may exist in certain types of initial positions, but only in a minority of cases. Even then it poses no different a problem than do lots of other positions - no Chess player has a smooth game every game.
Castling is a weird move to begin with, but especially in shuffle chess. However, we do support the other '960' rules. Bishops should be on different colored squares, and putting the king in between the rooks is a nice way to implicitly bar the king from the corner squares, where he would appear less than courageous at the start of the battle.
Note: All castling is 'CG-castling'
Using the Chess960 applet
Chess960 © Robert James Fischer
Java applet © Ed van Zon