شطرنج        CHESS

In my analysis of the Nakamura-NN simul game, I recommended 41...Rh8!



as an improvement on NN's 41...Rh7. Both moves have as their basic idea to play 42...Rdn, which leads to an easily drawn pawn ending (if White trades) or else lets the Black king get in front of White's f-pawn.

While neither 41...Rh7 nor 41...Rh8 is good enough for a draw, if White plays correctly, it's much harder for White to win after the latter move (though even after Black's inferior choice Nakamura immediately erred and allowed his opponent to reach a drawn ending). The difference is that the Black rook has sufficient checking distance from the White king, so the king cannot successfully approach the rook without allowing his f-pawn to be immobilized in variations like the one given to White's 42nd move: 41...Rhn 42.Kf4 Rfn+ 43.Kg3 Kc6 44.f4 Kc5 45.Rd1 Rgn+ 46.Kh4 Rfn 47.Kg5 Rgn+ 48.Kf6 and now if n=7, it's over, but if n=8, 48...Rf8+ forces the White king back and preserves the drawn position.

So if 42.f4 is bad against both 41...Rh7 and 41...Rh8, and if 42.Kf4 doesn't win either, how does White win? There are in fact two winning moves - neither of which is obvious (at least if you're not using external help!), and which I leave as an excellent exercise for the reader.

Solution in a few days.