Zugzwang - Zugzwang in Chess

Zugzwang in Chess

Hooper & Whyld 1992, p. 458

	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

White to move draws; Black to move loses Flear 2004, p. 11

	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

Black to move. Black is in zugzwang because he must move and lose the game

There are three types of chess positions:

1. both sides would benefit if it were their turn to move
2. only one player would be at a disadvantage if it were his turn to move
3. both players would be at a disadvantage if it were their turn to move.

The great majority of positions are of the first type. In chess literature, most writers call positions of the second type zugzwang, and the third type reciprocal zugzwang or mutual zugzwang. Some writers call the second type a squeeze and the third type zugzwang (Hooper & Whyld 1992) (Hooper 1970:196–97).

Normally in chess, having tempo is desirable because the player who is to move has the advantage of being able to choose a move that improves his situation. Zugzwang typically occurs when all the moves available are "bad" moves, tangibly weakening the moving player's position (usually from a draw to a loss or from a win to a draw) (Müller & Lamprecht 2001:22).

Zugzwang most often occurs in the endgame when the number of pieces, and so the number of possible moves, is reduced, and the exact move chosen is often critical. The diagram at top right shows the simplest possible example of zugzwang. If it is White's move, he must either stalemate Black with 1.Kc6 or abandon the pawn, allowing 1...Kxc7 with a draw. If it is Black's move, the only legal move is 1...Kb7, which allows White to win with 2.Kd7 followed by queening the pawn on the next move.

The diagram at below right is another simple example. Black, on move, must allow White to play Kc5 or Ke5, when White wins one or more pawns and can advance his own pawn toward promotion). White, on move, must retreat his king, when Black is out of danger (Flear 2004:11–12). The squares d4 and d6 are corresponding squares. Whenever the white king is on d4 with White to move, the black king must be on d6 to prevent the advance of the white king.

In many cases, the player having the move can put the other player in zugzwang by using triangulation; that article has an illustrative example. Zugzwang is very common in king and pawn endgames, where it is frequently achieved through triangulation. Pieces other than the king can also triangulate to achieve zugzwang – e.g., see the queen versus rook position at Philidor position. Zugzwang is a mainstay of chess compositions and occurs frequently in endgame studies.

Andy Soltis notes that many players do not appreciate zugzwang, thinking that it is an obscure concept that never occurs in their games. Without zugzwang, it would be very hard to win a chess game, even with an extra piece (Soltis 2009:15).