The answer is for white to first play d4. If black plays K-h5, white responds with Q-d3. Black is then forced to play either K-h4 or K-g4. Regardless, white plays Q-h3 and it’s checkmate. The other alternative after white’s opening move of d4 is for black to play K-g4, instead of the original K-h5, as in the first example. [...]