Black seems to defend
the critical h7 square but his position is cramped. White has
to proceed vigorously, even with sacrifices.
White's idea is based on a final Queen's sacrifice one move before the check mate.
The natural sequence 1.Bxf6
Bxf6 2.Rxh7 Nxh7
4.Nd2 Qf7 5.Ne4 Ke7 6.Qg6 Qxg6 7.fxg6 Rh8 is in Black's favor. However
White can first play an apparently innocuous intermediate move after
which the same sequencegives advantage to White.