In chess, a windmill (or seesaw) is a tactic in which a piece repeatedly gains while simultaneously creating an inescapable series of alternating direct and discovered checks. Because the opponent must attend to check every move, they are unable to prevent their pieces from being captured; thus, windmills can be extremely powerful. A windmill most commonly consists of a rook supported by a bishop.

Examples

Torre vs. Lasker

In the position diagrammed, from the game Carlos Torre–Emanuel Lasker, Moscow 1925, White sacrifices his queen in order to set up the windmill: Black must accept the sacrifice, as his own queen is unprotected, 25...g5 26.Qxh6 leads to unstoppable mate on g7 or h8, and any other attempt to stop the windmill would simply give White the queen. White gives discovered check by the bishop. White simply repeats the checking cycle, capturing as many pieces as he can with his rook. White concludes the windmill by taking the black queen. Black forked White's rook and bishop with 32... Kg6, but White still emerged three pawns ahead after 33.Rh3 Kxf6 34.Rxh6+ and went on to win.

Byrne vs. Fischer

The Game of the Century featured a windmill involving a knight and a bishop. The game continued from the diagrammed position as follows: Black sacrifices his queen in order to initiate an attack. Accepting the sacrifice allows Black to set up the windmill. Black emerges with an overwhelming advantage.