Zugzwang

Zugzwang is a chess term. It means a situation where any move by a player will weaken the player's position. The fact that the player is compelled to move means that their position will become significantly weaker.

For example...

Example of zugzwang

								[[Image:chess __ d44.png|22px|alt=h8 __|link=]]
								[[Image:chess __ l44.png|22px|alt=h7 __|link=]]
								[[Image:chess __ d44.png|22px|alt=h6 __|link=]]
								[[Image:chess __ l44.png|22px|alt=h5 __|link=]]
								[[Image:chess __ d44.png|22px|alt=h4 __|link=]]
								[[Image:chess __ l44.png|22px|alt=h3 __|link=]]
								[[Image:chess __ d44.png|22px|alt=h2 __|link=]]
	[[Image:chess d44.png|22px|alt=a1 black king|link=]]

{{{67}}}

Black to play

1. ... Kd7 and White cannot win:

2. c6+ Kc7

3. Kc5 Kc8

4. Kd6 Kd8 (opposing the king)

5. c7+ Kc8

6. Kc6 is stalemate

White to play

But if it is White to play in the original position, he can win by zugzwang:

1. Kc6! and now Black must move his king, for example

1..... Kd8

3. Kb7 and queens the pawn.

Mutual zugzwang

Either player to move loses

								[[Image:chess __ d44.png|22px|alt=h8 __|link=]]
								[[Image:chess __ l44.png|22px|alt=h7 __|link=]]
								[[Image:chess __ d44.png|22px|alt=h6 __|link=]]
								[[Image:chess l44.png|22px|alt=h5 black king|link=]]
								[[Image:chess d44.png|22px|alt=h4 black king|link=]]
								[[Image:chess __ l44.png|22px|alt=h3 __|link=]]
								[[Image:chess __ d44.png|22px|alt=h2 __|link=]]
								[[Image:chess __ l44.png|22px|alt=h1 __|link=]]

There are positions where either player to move will lose.

On the following diagram, Whichever king moves, he loses his pawn and the opponent will win the game.

History

The concept of zugzwang was known in the old forms of chess, like shatranj. We know this because there are some Arabic chess problems which use the idea.

The term itself comes from the 19th century in a German chess magazine. Its first use in English was in the early 20th century.