What is the missing piece (marked "?") in this configuration of a normal chess game?

BLACK

WHITE
Notice that the Black King is in check by the White Rook.

There are five white pieces and five black pieces, and one additional white piece or black piece removed and captured from the board.

As the black king is in check by one of two stacked rooks, the only possibility is that a pawn at c7 revealed the check by capturing a black piece at d8 and was promoted to a rook. The captured piece on the black square could not have been a black queen or black rook as the white king would have already been held in check. The piece captured, then, must have been either a black "black-square" bishop or black knight. Since the starting black "black-square" bishop's escape route never opened, i.e., the black pawns at e7 and g7 are unmoved, the black "black-square" bishop at f8 must have been previously captured, and since there are two black knights on the board the h7 black pawn must have been promoted to either a "black-square" bishop or knight.

The missing piece at h4 can also not be a black rook or black queen as, again, the white king could not already have been held in check. In addition, it cannot be the black (or the white) "white-square" bishop as the h4 square is black. Therefore, since the missing piece cannot be black (with all black pieces now eliminated from the possibility) the piece must be white.

The b7 black pawn must have captured a white piece at a6 - a white square; and the f7 black pawn must have captured three white pieces at e6, d5 and c4 - all white squares. For the h7 black pawn to have been promoted, it needed to either capture one or two pieces. Yet, only five white pieces could have been captured and four of the five white pieces are accounted for, thus only one piece was captured by the h7 black pawn. The capture would have to have been at G2 - a white square - in order for the h7 black pawn to have been promoted to the piece (or same as the piece) captured at d8. The missing sixth piece must then be the white "black-square" bishop, as all the other captured white pieces were on white squares.

Posted by Dej Mar on 2008-06-12 21:02:11