Kriegspiel (chess) - Kriegspiel Problems

Kriegspiel Problems

Jacques Rotenberg
The Problemist 1976

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Kriegspiel, mate in 8. Black has a bishop somewhere on dark squares, not exactly known where.

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 Kriegspiel problem is shown at the right. White must checkmate Black in 8 moves, no matter where the black bishop initially is (it is somewhere on dark squares) and no matter what black plays. (Note that in a real game, black would not see white's moves, but for a problem in which white is to force a win, one must assume the worst-case scenario in which black guesses correctly on each move.) For example, 1. Ra1?? is a draw by stalemate if the black bishop was initially on a1. 1. Nf2 Bxf2 2. Kxf2 (or Rxf2) is stalemate as well. So, white should not move either the knight or the bishop, because either might capture the black bishop by accident. For the same reason, the white rook should move only to light squares -- but only half of the light squares are reachable without visiting a dark square along the way.

The solution is the following. White tries to play 1. Rg2.

• If this move is not possible (umpire says No), then the black bishop must be on b2, d2 or f2. In this case white can instead play 1. N(x)f2# (checkmate).
• If the move is possible, it is made and then black moves the bishop. White still doesn't know where the bishop is.

White continues with 2. Rg8.

• If not possible, then black bishop is on g3, g5 or g7. White plays 2. Be5. If black now plays 2...Bxe5, 3.Nf2#. Otherwise (any move by black) 3. Nf2+ Bxf2 4. Rxh2#.
• If possible, white continues 3. Rh8. (This is safe -- the black bishop can't be on h8 to be captured, because it wasn't on g7 on the previous turn.) 4. Rh5 5. Rb5 (if not possible, 5. Rh3 and 6.Be5). 6. Rb1 7. Nf2+ Bxf2 8. Kxf2#.