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WITH four pawns only one step from promotion, today's position, a study by Korolkov, takes time to digest, but once you get into the swing of the solution, it positively gallops along.

It is White to play and win, but his first priority is to avoid losing: Black threatens mate in two with 1 . . . c1=N+ 2. Ka1 Ndb3. None of White's pawn promotions helps, so he must begin with a check. Having worked out that 1. Nef6+ or 1. Ndf6+ get nowhere after 1 . . . Kh4] we have only one more check left to look at, so the solution is ready to roll.

After 1. Nf4+ Black does not want the white d-pawn to queen with check. 1 . . . Kh4

2. d8=Q+ Kg3 3. Ne2+ and 4. Qxd2 or 1 . . . Kg5 2. d8=Q+ Kxf4 3. Qxd2+ win easily for White, so it has to be 1 . . . Kh6.

White must check again (2. Ne2 loses to 2 . . . Bf7+ 3. Ka1 Bd4+ with mate to follow), so it has to be 2. g8=N+, when Kh7 is forced.

Now White's horses must tread carefully to avoid each other's hoofs. The wrong way is 3. Nef6+ Kg7 4. Ne6+ Kh8 and the checks run out. So the right path must be 3. Ngf6+ Kh6 (3 . . . Kh8 4. Nxg6 is mate) 4. Nxg4+ Kh7 and only now 5. Nef6+. Now the back rank is cleared, so after 5 . . . Kg7 6. Ne6+ Black cannot retreat to h8 without allowing a fatal promotion to a queen.

So it has to be 6 . . . Kf7 when you should be able, by a process of extrapolation if nothing else, to work out the final two moves. (Solution tomorrow.)