The first thing to note is that Black's king is very restricted. Its only move, Kd5, pins the rook and allows mate by Qd4. The bishop on f7 is also tied down: if it moves, then Qc5 is mate. The other bishop cannot move to g1 or g3 without allowing Rh5 mate, and Bf4 again allows Qc5 mate by blocking the king's flight square.
That leaves the rook. Again Rf4 allows Qc5 mate, while most other rook moves are mated by Nxf7. The only move left for White to cope with is Re2+ (which would again be mated by Nxf7, if White were not in check).
Pausing only to notice the clever points that 1. Rxf7 (threatening Qc5) is met by Rc4] and 1. Rf1 (same threat) is met by Bg1] we should by now have the idea of solving it with a king move, escaping the check on e2 and forcing Black to commit suicide.
Moves to the b-file are ruled out by Rb4+, Kd2 allows Bf4+ and Kd3 lets Black stave off mate by Re3+, so that leaves 1. Kd1] which is the answer. 1 . . . Re1+ is met by Rxe1 mate, and 1 . . . Rd4+ allows cxd4 mate. The rest we have already worked out.
The problem is a good example of a waiting key. White's 1. Kd1 carries no direct threat of mate, but he cannot keep his perfect defensive position intact. The construction is neat but Black's Re2+ possibility in the starting position is a clear signpost to the solution.Reuse content