Chess Tactic - Zugzwang

Zugzwang (German for compulsion to move) occurs when a player is forced to make an undesirable move. The player is put at a disadvantage because he would prefer to pass and make no move, but a move has to be made, all of which weaken his position. Situations involving zugzwang occur uncommonly, but when they do occur, it is almost always in the endgame, where there are fewer choices of available moves.