960

What is 960 Chess

Chess960, also called Fischer Random Chess (originally Fischerandom), is a variant of chess invented and advocated by former world chess champion Bobby Fischer, announced publicly on June 19, 1996, in Buenos Aires, Argentina. It employs the same board and pieces as standard chess, but 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 instead 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.

In 2008, FIDE added Chess960 to an appendix of the Laws of Chess.

Starting position requirements

White's pieces (not pawns) are placed randomly on the first rank, with two restrictions:

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 standard chess.

Why 960?

Each bishop can take one of four squares; for each setup of two bishops, the queen has six possible squares; finally, the two knights can assume five and four possible squares, respectively. This leaves three vacant squares which the king and rooks must occupy, per setup rules, without choice. Therefore there are 4×4×6×5×4 = 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 1920÷2 = 960. (Half of the 960 positions are left–right mirror images of the other half; however, the Chess960 castling rules preserve left–right asymmetry during play.)

Castling

As in standard chess, each player may castle once per game, 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 king and rook. After castling, the final positions of king and rook are exactly the same as in standard chess

Castling prerequisites are the same as in standard chess, namely:

The king and the castling rook must not have previously moved, including having castled.

No square from the king's initial square to its final square may be under attack by an enemy piece.

All the squares between the king's initial and final squares (including the final square), and all the squares between the rook's initial and final squares (including the final square), must be vacant except for the king and rook.

A recommended way to castle that is always unambiguous is to first move the king outside the playing area next to its final square, then move the rook to its final square, then move the king to its final square.

960 Opening Principles

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 that can be attacked on the first move. The Stockfish program rates the Chess960 opening positions between 0.1 and 0.5 pawns advantage for White, while the mean value for the same in standard chess is 0.2.[citation needed]

It has been argued that two games should be played from each starting position, with players alternating colors, since the advantage offered to White by some initial positions may be greater 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 moves for White to attack, and there are no unprotected pawns.

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