The sequence here starts in standard fashion: 1. Bxh7+, Kxh7 (Black is better off declining the sacrifice, but assume he accepts it); 2. Ng5+—and now suppose Black plays Kg6. White has to add pressure fast, but how? The king’s move to g6 not only takes it out of danger of being mated on the back rank; it also guards h5 and so prevents White from moving his queen there. The best bet usually is to bring your queen in at g4 or d3 (and then from d3 to g3); the idea is to get your queen behind your knight and thus prepare a discovered check when your knight moves. Another possibility is to use the h-pawn, as White does here with h4-h5+, creating the position that follows in the next frame....