Solution to chess problem number 5
The theme of this problem is a combination of a double Grimshaw with two unpins of the white queen. In a Grimshaw two black pieces, here the rook and bishop, each move to the same square (in different variations) and in doing so mutually interfere with each other thus simultaneously preventing the full action of each piece. White exploits this to deliver mate and in two of these interferences the white queen is also unpinned and becomes free to deliver the mates. The first two variations of the solution comprise one Grimshaw, the next two the second Grimshaw.
Key move 1. Bd7 threat 2. Rg4 mate.
1...Re6 2. Qf4 mate.
1...Be6 2. Bf6 mate.
1...Rc4 2. Qd5 mate.
1...Bc4 2. Bc1 mate.
Other variations are 1...gxh5 2. Rxh5 mate, and 1...Bxf7+ 2. Nxf7 mate.