With the f-pawn as good as dead, White's only hope of winning must involve promoting the b-pawn, so 1. b6 is the obvious move to consider. Black's knight is too far away to control b8 in time, but there is a prospect of a fork on c6, so our analysis goes 1. b6 Nf3 (or Ng4) 2. b7 Ne5 (Nd4 would lose to 3. Kb6) and now White must stop to think. After 3. Kb6 Nd7+ 4. Kc7 Nc5] Black forces a draw and 4. Kc6 Nb8+ 5. Kc7 Na6+ also makes no progress. Eventually we have to give up the whole idea and go back to the starting position. The only other hope is to bring the king round to try to cut off the black knight's return.
It hardly looks a serious try, but the right move is 1. Kb6]] Black's knight must set off immediately since 1 . . . Kxf5 2. Kc7 leaves him unable to stop the b-pawn. So play starts 1. Kb6 Ng4 2. Kc7 when Black must choose between Nf6 and Ne3. The first is more easily dealt with: 2 . . . Nf6 3. Kd6] Ne4+ 4. Kc6 Nd2 5. Kd5] Nb3 6. b6 Na5 7. Ke6] The b-pawn is held, but now the f-pawn wins for White.
2 . . . Ne3 is much more fun: White plays 3. Kd7] Nd5 (3 . . . Nc4 is met by 4. Ke6) 4. Kd6 Nb6 5. Ke6. White is half-way there, but after 5 . . . Kh6] 6. f6 Kg6] considerable delicacy is still needed, since 7. f7? Kg7 8. Ke7 Nd5+ 9. Ke8 Nf6+ 10. Kd8 Nd5 leads to a draw. The trick involves losing a move: 7. Ke7] Nd5+ 8. Kd6 Nb6 9. Ke6. Now it's Black's turn to play and 9 . . . Nc8 loses to 10. f7 Kg7 11. Kd7 Nb6+ 12. Ke8. So Black plays 9 . . . Kh7 (to get back on track with 10. f7 Kg7) when the final touch is 10. Ke7] Nd5+ 11. Kd6 Nb6 12. Kc6]] Nc4 13. Kd7 Kg6 14. Ke7 winning after 14 . . . Nb6 15. f7 or 14 . . . Ne5 15. b6. This brilliant composition contains almost all the lessons the practical player needs to know about the battle between a king-assisted passed pawn and a knight.
Meanwhile, back in the world of real chess, Fide have announced the pairings for the next round of the world title eliminators. Gata Kamsky will play Viswanathan Anand, Boris Gelfand meets Vladimir Kramnik, and Valery Salov plays against Jan Timman. The three winners will be joined in the semi-finals by Anatoly Karpov.
The draw for the last eight of the rival PCA championship, backed by Intel, will be announced this week.