because he has to make a move
– the player would prefer to pass and make no move.
The fact that the player must make a move
means that his position will be significantly weaker
than the hypothetical one in which it is his opponent's turn to move.
A player whose turn it is to move
who has no move that does not worsen their position is said to be in zugzwang.
In a chess endgame, being in zugzwang
usually means going from a drawn position to a loss
or a won position to a draw, but it can be from a win to a loss,
or a substantial loss of material which probably affects the outcome of the game."
I have studied the enemy all my life.
I have read the memoirs of his generals and his leaders.
I have even read his philosophers…
I have studied in detail the account of every damned one of his battles.
I know exactly how he will react under any given set of circumstances,
and he hasn’t the slightest idea of what I’m going to do.
So when the time comes, I’m going to whip the hell out of him.
George S Patton
"Zugzwang is when a chess player's choices
all result in a worse position than having done nothing
which isn't a choice."