Los Alamos chess

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a b c d e f
6 a6 black rook b6 black knight c6 black queen d6 black king e6 black knight f6 black rook 6
5 a5 black pawn b5 black pawn c5 black pawn d5 black pawn e5 black pawn f5 black pawn 5
4 a4 b4 c4 d4 e4 f4 4
3 a3 b3 c3 d3 e3 f3 3
2 a2 white pawn b2 white pawn c2 white pawn d2 white pawn e2 white pawn f2 white pawn 2
1 a1 white rook b1 white knight c1 white queen d1 white king e1 white knight f1 white rook 1
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Los Alamos chess

Los Alamos chess (or anti-clerical chess) is a chess variant played on a 6×6 board without bishops. This was the first chess-like game played by a computer program. This program was written in Los Alamos laboratory by Paul Stein and Mark Wells for the MANIAC I computer in 1956. The reduction of the board size and the number of pieces from standard chess was due to the very limited capacity of computers at the time.

The computer played three games. The first it played against itself. The second one was against a strong human player, who played without a queen. The human player won. In the third game, MANIAC I played against a novice chess player who had been taught the rules just before the game. The computer won, marking the first time that a computer had beaten a human player in a chess-like game.


The starting position is shown on the right. All rules are as in chess except:

  • There is no pawn double-move, nor is there en passant capture;
  • Pawns may not promote to bishops;
  • There is no castling.

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