Kriegspiel (chess) follows. The game is played with three boards, one for each player; the third is for the umpire (and spectators). Each opponent knows the exact position of just their pieces, and does not know where the opponent's pieces are (but can keep track of how many there are). Only the umpire knows the position of the game. The game proceeds in the following way: The umpire announces: Pawn promotions are not announced. Kriegspiel is sometimes used in chess problems. In these, usual variations introduced by different black moves are replaced by variations introduced by different announcements. An example of a
Janus Chess checkmate cannot be . Due to the extra pieces, each player starts the game with considerably more " power" compared to standard chess; however, the game has only a slightly higher material "power density", since there is more room for players to maneuver pieces because of the larger board (10×8 = 80 squares). Due to the different board and pieces, players are unable to use normal chess opening theory, and chess tablebases have limited value in the endgame. Janus Chess has been popular in Europe with regular tournaments drawing strong players. Several chess grandmasters have played this game including Viktor