A neat solution, involving under-promotion. All black’s moves are forced. [Result "1-0"] [FEN "8/1KP5/8/2p5/1pP5/p7/k7/1R3R2 w - - 0 1"] [SetUp "1"] 1.c8=B$1 {As in all good chess puzzles, this is the only move which forces mate in the required number of moves. Some close tries are as follows… } (1.c8=Q b3 2.Rfc1 ({or} 2.Rb2+ Kxb2 3.Qh8+ Kc2 {and the king survives immediate checkmate})2...b2 3.Qh3 bxc1=N$1 {preventing mate next move}) (1.Rf2+ Kxb1 2.c8=Q b3$1 {preparing to give the king a shelter on a2} 3.Qg4 ({or} 3.Qf5+ Ka1 {and the rook blocks the queen}) 3...b2 {and there is no mate}) b3 2.Bg4$1 b2 3.Bd1$1 {The key move, preventing the king’s escape via b3 and allowing the following capture. If white had promoted to a queen on move 1 this position would now be stalemate!} 3...Kxb1 4.Bb3+ {A tidy finish, with the rook and bishop mating the king} 1-0 You must activate JavaScript to enhance chess game visualization.
