Positional Sacrifices Aren't Just to Draw

Until now, all of the examples of Petrosian's Exchange Sacrifice have been sacrifices to achieve a draw, at times with some winning chances. Petrosian also gave examples of sacrifices to achieve the win.

Looking at the diagrammed position, Black is better. The move that many players would choose without much thought is 19...h6. Petrosian played the surprising 19...Rxe4 instead. If White now captures on e4, the Black light-squared Bishop will be unopposed on the long diagonal, when the opening of the Kingside with ...h6 will be even stronger.

White played 20.c4, which is also surprising until you notice 21.Nc3, threatening to capture the Rook with the Knight, when the Rook can't retreat to b4. Now the idea 20...h6, is even stronger than a move earlier.

USSR School Championship 1946
Petrosian, Tigran

Dunaev, Vladimir
(After 19.b2-b3)
[FEN "4k2r/2qnbppp/p1bpp3/P1p3P1/Nr2PP2/1P2BB2/2PQ3P/R4RK1 b k - 0 19"]

White continued 21.g6, and Petrosian commented

This move is bad; my opponent was young and inexperienced. He should have played 21.Nc3 Rxe3 22.Qxe3 hxg5 23.fxg5 Ne5 24.Bxc6+ Qxc6, although Black would be more than compensated for the exchange.

The game continued 21...f5 22.Nc3 Nf6 23.Bxe4 fxe4 24.Rad1 (Better is 24.f5, 'fighting for the square d5'.) 24...d5 25.cxd5 exd5 and Black soon won.

To play through the complete game see...

Dunaev vs Tigran Vartanovich Petrosian, USSR 1946
http://www.chessgames.com/perl/chessgame?gid=1106130

...on Chessgames.com.