Los Alamos Chess

Chess variant

Chess variant on a 6x6 board with no bishops.

Otherwise the rules of chess apply, with the following differences:

Pawns have no double-move option.
Pawns cannot promote to bishop.
Castling: the rook always moves two, and the king moves one or two fields (see diagram below).

Los Alamos researchers, 1956 (this was the first chess played by a computer software)^[wiki]