In chess an exchange sacrifice occurs when one player gives up a rook for a minor piece (a knight or bishop). It is often used to destroy the enemy pawn structure (as in several variations of the Sicilian Defence where Black plays RxNc3), to establish a minor piece on a strong square (often threatening the enemy king), to improve one's own pawn structure (creating, for example, connected passed pawns), or to gain time for development. Tigran Petrosian, the world Champion from 1963-1969, was well known for his especially creative use of this device; in the game Reshevsky-Petrosian, Zurich 1953, he sacrificed the exchange on move 25, only for his opponent to sacrifice it in return on move 30 (the game ended in a draw); this game is perhaps the most famous and most frequently taught example of the exchange sacrifice.