1 d8(N) is forced, since White must prevent a bishop check on the long
diagonal. After 1...Be8 2 a6 Bg6, the threat is on again, and this time
the only move is 3 e8(R)! since after 3 e8(Q) Be4+ 4 Qxe4 Black is
stalemated. 3...Bxe8 4 a7 Bg6 puts it on again, but 5 a8(B)! stops the
checks and wins. Underpromotion to a knight, rook, and bishop in five
moves is quite a feat.