Daily chess puzzle: 20th anniversary (2)

A follow on from yesterday’s puzzle.

Why doesn’t 1…f4 win, when 1…Bg3!, with the same idea, does?

Kramnik v Bareev, Kazan 29/12/1997

Solution

The position is all about move orders. 1…f4? is similar in intent to 1…Bg3, to bust open the f file, but 1…f4 2 ef (or 2gf, transposes) Bf4 3 ef Rf4

4 Re8+ Kf7

The critical position

And it is all going so well for Black, except for 5 Nd6+!!, the move I missed, and at best it is a draw. Black can easily lose, either his Rf4 or be mated.

My analysis, using the more colourful, readable design of the new ChessBase 14, is shown below. 5 Nd6+ is a desperado, and so in practice many people would find it if faced with the position, but its strength was a surprise to me. Black has a narrow path to a drawn Q+P ending.

FEN

5rk1/p1p3pp/3b3q/5p1r/1PNP4/P3PQP1/6P1/R3R1K1 b – – 0 24