The striking key 1.Rf7! threatens 2.Ba2+ Kxc2 3.Rxf5, forcing 3...Kd3
4.0–0–0#. Black has seven possible rook moves. Six of them fail to the
same idea – a bishop discovered check, followed by capture of the rook, forcing
the same mate as in the threat, eg.
1...Rxc5 2.Ba2+ Kxc2 3.dxc5 Kd3 4.0–0–0#;
1...Rd5 2.Ba2+ Kxc2 3.Bxd5 etc;
1...Re5 2.Ba2+ Kxc2 3.dxe5;
1...Rxf7 2.Ba2+ Kxc2 3.Bxf7;
1...Rf6 2.Ba2+ Kxc2 3.Rxf6;
1...Rf4 2.Ba2+ Kxc2 3.Rxf4.
Note that the threatened Rxf5 capture never actually happens in any of these
variations. The other black rook move is met by immediate capture of the rook,
followed by an unexpected battery mate: 1...Rg5 2.Bxg5 h4 3.Rxf3 exf3 (3...h3 4.Se2#)
4.e4#