Today we are going to talk about a relatively common positional exchange sacrifice - Rxe6 (or Rxe3 for Black). As a rule, a player achieves two main goals with such a sacrifice: 1) eliminates the opponent's Bishop and therefore completely dominates on the light squares (or dark squares for Black). 2) makes the position of the opponent's King more vulnerable.
Even though this concept is pretty simple, it was virtually unknown even for the World's best players before WWII. In cases where they sacrificed an exchange positionally, the resulting attack was so strong that the outcome of the game was never in question. Look at the next famous example. Even though technically the Rxe6 sacrifice was positional, in reality White attack was so strong and irresistible that I cannot even call the Rxe6 move a sacrifice!
Enter Tigran Petrosian and Ulf Andersson. These two great chessplayers are well known for their positional exchange sacrifices. I will never forget the story which was told by an older master who played against the great Petrosian. It was the King's Indian Defense and at some point a part of the position looked like this ( the material was even, but I don't recall the exact position):
So, the master who played Black asked Petrosian why he didn't play Bg5 (remember that there were many other pieces, including Queens, so the Bg5 move made sense). Petrosian smiled and said that he figured out Black's cunning trap. "What trap??" asked the master in amazement. "You would trap my Bishop by playing Rf4! Then you play h6 and force me to capture your Rook by Bxf4 so after exf4 your Bg7 becomes very active and points at my King."
Here is one of Petrosian's iconic exchange sacrifices:
The following games of Ulf Andersson against two great World Champions are similar to some extent. In both of them he sacrificed an exchange on e3 in the early middle game to dominate on the dark squares. But the similarities end here. While Kasparov skilfully neutralized Black's initiative and Andersson suffered throughout the whole game and was lucky to escape for a draw, Karpov's game was different. The black pieces were so active there that the World Champion had to return the exchange but still he wasn't able to save the game:
In the second part of this mini-series we'll see how modern Grandmasters incorporate this sacrifice in their games, some of them so frequently
that it is really 'business as usual.'