There is only one player

who is not seeing the chess board.

In this Game.

WAR GAME

Kriegspiel

Kriegspiel ('War game') is an unorthodox chess game in which the players only know for certain the moves of their own pieces. They have to deduce where the opponent's pieces are by questioning an umpire. It is played on three boards with partitions between them. The umpire sits with the middle board with the true position. Players are permitted to ask two kinds of question. "Can I move here?" and "Are there any?" (meaning pawn captures). The umpire replies accordingly. Checks and captures are announced by the umpire, and provide more clues. The game was invented by Henry Michael Temple (1862–1928).[1]p211[2]

The umpire may have been AngleFire