You're White in the above position and you've just played 23.Qc3 supporting the bishop in an attack on g7. Your opponent plays 23...axb5. How do you recapture: a) get on with the attack with 24.Bxg7; b) avoid any nonsense by playing 24.axb5; c) open the c-file with 24.cxb5?

The position comes from Kasparov-Polgar, Linares 1997, and is a fine demonstration of a world champion's cold rationality. Since White has gone to the trouble of attacking g7, the consistent move would seem to be 24.Bxg7, but after 24...b4! 25.Qb2 Rxa4 26.Bxf8 Bxf8 Black has a good game. In that case, the logical plan seems to be 24.axb5, forcing Black again to think about the defence of g7.

Instead of that, however, Kasparov calmly exchanged queens with 24.cxb5, even losing a pawn in the process. He knew, however, that Black's b-pawn was doomed and his K-side pieces would never escape from their bind. The whole game is a model of tight control by the champion.

White: Garry Kasparov

Black: Judit Polgar

1 e4 c5 22 Bd4 Ra8

2 Nf3 e6 23 Qc3 axb5

3 d4 cxd4 24 cxb5 Qxc3

4 Nxd4 Nc6 25 Rxc3 Rxa4

5 Nc3 Qc7 26 Rc7 Bg5

6 Be2 a6 27 Bf2 b6

7 0-0 Nf6 28 Rb7 Ra2

8 Be3 Bb4 29 Bf1 Rb2

9 Na4 Bd6 30 f4 Bf6

10 g3 Be7 31 Rxb6 Bc3

11 c4 d6 32 Rb7 g5

12 f3 Bd7 33 f5 Bb4

13 Rc1 0-0 34 f6 h5

14 Nxc6 Bxc6 35 Rc1 Kh7

15 Nb6 Rad8 36 Rb8 d5

16 b4 Qb8 37 exd5 Bd6

17 b5 Be8 38 Rd8 Be5

18 a4 Nd7 39 Rcc8 Bxb5

19 Nxd7 Rxd7 40 Bxb5 Rxd8

20 Qb3 Qc7 41 Bd3+ resigns

21 Rfd1 Rd8