16 July 2012

Glossary of Tactics: Zugzwang

The term Zugzwang means compulsion to move. It refers to positions that arise in which the player to move must weaken his or her position. If it were possible to pass in chess, the position might remain secure. But every available move creates vulnerabilities.

Zugzwang is a common theme in endings, and is easy to understand in certain pawn endgames. In these two illustrative positions, the player to move must lose a pawn. In the first, loss of this pawn loses the game. In the second, the game remains drawn with correct play.

These theoretical patterns occur in real games, such as in one of my recent tournament games. Black resigned because after the moves 38...a4 39.a3, his king must abandon his e-pawn, losing it and the f-pawn.

Black to move

Zugzwang can appear in endgames with other pieces.

White to move

Black's rook guards the pawn, but can be attacked on its present square by the white king moving to e7. The rook's only escape from the king is d5.

White wins by triangulation.

1.Ke8! Rd5 2.Ke7

Black is now in zugzwang. The rook cannot return to d6 and so must abandon the pawn. 2...Rd1 loses more quickly to 3.Qb3+, forking king and rook.

Endings of rook versus minor piece are often drawn unless the player with the rook can put the other in zugzwang. It is easier to force such positions against the knight than against the bishop.

Black to move

Black must give up defense of the knight. If it were White to move, the rook slides over one square in either direction, maintaining the pin and transferring the move to Black. Giving up a tempo is often how one player places the other in zugzwang.

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