Chess: Putting a value on a bishop

BISHOPS and knights, they tell us, are worth three pawns apiece, while rooks are worth five and queens nine. In reality, the exchange rates fluctuate wildly.

Everything depends on the effectiveness, both immediate and potential, of each particular piece. So a rook and pawn, for example, may be full value for a bishop and knight in an endgame, where there are wide open spaces for the rook to operate freely, but in an average middle-game the pair of minor pieces will be too much for the lumbering rook.

The game between Gata Kamsky and Paul van der Sterren, which finished yesterday after being adjourned on Monday night, provided a fine example of fluctuating exchange rates.

After the opening moves 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. 0-0 Be7 6. Re1 b5 7. Bb3 d6 8. c3 0-0 9. h3 Nb8 10. d4 Nbd7 11. Nbd2 Bb7 12. Bc2 Re8 13. Nf1 Bf8 14. Ng3 g6 15. b3 Bg7 16. d5 Nb6 17. Be3 Rc8 18. Qe2 c6 19. c4 cxd5 20. cxd5, van der Sterren sacrificed a piece for two pawns with 20 . . . Nbxd5 21. exd5 Nxd5.

But, as Bent Larsen is prone to remark in such positions, they are not just two pawns, they are two centre pawns. The prospect of Black's d-, e- and f- pawns rolling down the board provides excellent value for the piece. So instead of holding on to his extra material, Kamsky sacrificed his queen: 22. Be4]? Nc3 23. Bxb7 Nxe2+ 24. Nxe2.

White now has three pieces for queen and two pawns, so Black is nominally two pawns ahead. But if the white bishop is allowed to settle on d5, the extra black pawns will become worthless, and White's minor pieces will pose a swarm of unpleasant problems.

So van der Sterren gave up his rook for a bishop: 24 . . . d5] 25. Bxc8 Qxc8 26. Rac1 Qa8. It is now rook and two knights for queen and two mobile pawns, both of which add up to 11 on official rates and it is hard to say who stands better.

Later, at the cost of another pawn, Kamsky created serious attacking threats, forcing van der Sterren to return his queen for rook and knight. The result was an endgame of bishop and four pawns against bishop, knight and one pawn; again nominally equal, but van der Sterren's two connected passed pawns were enough for him to convert the position into an equalising win.

Current scores in Wijk aan Zee, the Netherlands, are: Gelfand 1 Adams 1; Kamsky 1 van der Sterren 1; Timman 11 2 Lautier 1 2 ; Anand 11 2 Yusupov 1 2 ; Khalifman 1 2 Salov 11 2 ; Kramnik 11 2 Yudasin 1 2 . The second Gelfand-Adams game was a short and correct affair, with Gelfand playing White and achieving very little from an opening that began 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d3 d6. The third games will take place today.