This week’s problem is a selfmate. White, to play, must force a reluctant Black
to mate him. The battery along the g-file suggests the solution may involve luring
the black knight away, but how precisely?
The idea is that a rook move down the b-file will threaten 2.Qf6+, forcing 2...Sxf6
with discovered check and mate. Black will defend by moving his knight from g4. But
which square should the rook go to? Thus, we have the tries 1.Rb6? Sf2!; 1.Rb4?
Sxe5!; and 1.Rbb8? Sf6!.
The key is 1.Rb5! Threat 2.Qf6+ Sxf6, with the variations 1...Sf2 2.Qg5+ Rxg5#;
1...Sxh6 2.Sxf5+ Sxf5#; 1...Sf6 2.Re8+ Sxe8#; 1...Sxe5 2.Sc6+ Sxc6#.