This position came up in a recent blitz game at Delaney's Coffee Bar, a popular meeting place for chessplayers in West Vancouver, B.C. It is White (Dadian) to play. It was obvious to me that Black's situation is critical and in fact I was looking for the best way to finish things off.
All of White's previous play has been aimed at conquering h7. It may appear that success is at hand, but there is a problem. When the knight on h5 moves away, Black will capture on f6 and defend the mate. And if White sacrifices a piece somewhere, Black will have the defensive resource Bc5-f2+, returning the piece and exchanging queens. On top of that Black is threatening a5-a4.
After a few seconds' reflection (this is a blitz game, remember) I noticed my hand reaching out to defend the f-pawn with 1.Rf1?! My opponent immediately went wrong with 1...Rad8? and after 2.Rxd8 he was soon forced to resign because of a general collapse on f7.
The next day I reconstructed the position and started looking for the best line for White. It turns out that mate on h7 is a chimera of sorts. In the diagram position White should abandon the original focal point and shift his attention to g7.
The threat is obvious: 2.Nxf7+ Rxf7 3.Bxf7 Qxf7 and now 4.Qg7+ followed by 5.fxg7 mate. This is how things would go after, say, 1...a4? Instead, Black must get off the mate by clearing g8 for his king:
Now White can win the exchange with 2.Ne6!? fxe6 3.Qg7+ Qxg7 4.fxg7+ Kg8 5.gxf8+ Rxf8 6.Bxe6+ Kh8 but then Black's bishop pair would give him quite a bit of compensation. Happily for White there is something stronger:
Black's reply is forced because of the continuing threat of Qg7 mate.
2...Rxf7 3.Bxf7 Qxf7
The first wave of the assault appears to be over, and White has given up a rook for two bishops. He must press his attack before Black can consolidate.
4.Qg7+! Qxg7 5.fxg7+ Kg8 6.Rd7!
The point of White's combination. Black's king is short of squares and is facing a deadly check on f6. Playing the rook to f8 doesn't help so there is only one defensive try left:
With Black's knight cutting off the defence of White's g-pawn, it is starting to look like White's attack has run out of steam. To renew the threat of Nf6+ White must protect the g-pawn with his other rook. The square g1 is covered, so there is only one way forward:
The beauty of this move is that White can calmly leave his important-looking d7 rook to be taken after, say, 7...Bc8. With Black's king completely entombed, 8. Rg2 will renew the threat of mate with Nf6. Black must rush over a piece to defend f6 against the deadly check, and his rook on a8 is the only viable candidate.
7...Re8 8.Rg2 Re6
Black's defensive exertions have prevented an immediate mate, but they have also weakened his back rank. This adds a final resource to White's arsenal:
The rook cannot be captured because of 9...Kxf7 10.g8Q+, so White recovers a piece. He is now up the exchange and is threatening 10.Rd7 with further destruction. There are no realistic defensive chances left and Black can safely resign.
I hope the reader has enjoyed these variations as much as I did while working them out.