Zugzwang
Every move makes things worse. Make them move.
Example
Black has to move, and every move gives ground.
- 1... Kf8: If the king steps aside…
- 2. Kd7: …White's king takes the key square.
- 2... Kf7
- 3. e6+
- 3... Kf8
- 4. e7+
- 4... Kf7
- 5. e8=Q+: The pawn queens.
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