1.Ra3!
A double-edged sacrificial move, defending against the mate threat on a1 and opening the d1-h5 diagonal for the queen
1...	bxa3
2.Bd7!
Another move which exposes the Black king with a gain of tempo: 2.Bxc8 Rxc8 3.Rxh7+ Kxh7 4.Qh5+ Kg8 5.Qg4+ Kf8 6.Qxc8+ Qe8 isn't good enough
2...	Qxd7
3.Rxh7+	Kxh7
4.Qh5#
Sokolov-Mikhailov (1973)