Positional Exchange Sacrifice

Petrosian was known for his use of the positional exchange sacrifice, where one side sacrifices a rook for the opponent's bishop or knight. Kasparov discussed Petrosian's use of this motif, "Petrosian introduced the exchange sacrifice for the sake of 'quality of position', where the time factor, which is so important in the play of Alekhine and Tal, plays hardly any role. Even today, very few players can operate confidently at the board with such abstract concepts. Before Petrosian no one had studied this. By sacrificing the exchange just like that, for certain long term advantages, in positions with disrupted material balance, he discovered latent resources that few were capable of seeing and properly evaluating."

One of Petrosian's most famous examples of the positional exchange sacrifice is from his game against Samuel Reshevsky in Zurich 1953. In the above puzzle, Reshevsky, playing white, appears to have an advantage due to his strong pawn center, which may become mobile after Bf3 and d4–d5. Petrosian, realized he was in a difficult position because of the passive placement of his pieces, relegated to defensive roles. He further understood that White might also advance on the kingside with h2–h4–h5, provoking weaknesses that would make it more difficult to defend later on. Faced with these threats, Petrosian devised a plan to maneuver his knight to the square d5, where it would be prominently placed in the center, and blockade the advance of White's pawns. So Petrosian played 25... Re6! in that puzzle. With the rook vacated from e7 (clearance), the black knight is free to move to d5, where it will be attacking the pawn on c3, and help support an eventual advance of his queenside pawn majority with ...b5–b4.