Mate in 2

Observe that if White were to pass their turn, a mate is prepared for every legal Black response: 1...Kh4 2.Rxh6#, 1...Qxg6 2.Qh3#, and 1…Q anything else 2.Qxg5#. In such cases, the key is usually a waiting move, one that either preserves the set mates or alters one or more of them.

The piece best suited to wait without disturbing the status quo is the wK (1.h3? almost works — 1...Kh4 2.Qg4# and 1...Qh7/Qh8/Qg7/Qf8 2.Qxg5# — if not for 1...Qxg6!). But where should it move? Most options can be eliminated immediately as they run into checks; for example: 1.Ke6? Qxg6+!, 1.Kc5? Qf8+!, etc. Moreover, 1.Ke4? is refuted by 1...Qxg6!, pinning the wQ. This leaves 1.Kc4! as the only choice — and it indeed is the key.

The subsequent variations are purely a repetition of the set play outlined above. However, we revisit them to bring the Black Correction involved into focus: moving the bQ randomly (1...Q~) unguards g5 (primary error), allowing 2.Qxg5#; the correction, 1...Qxg6, keeps g5 defended but self-blocks the g6 square (secondary weakness), leading to 2.Qh3#; and finally, 1...Kh4 is met by 2.Rxh6#. To hark back to the try 1.h3, note that it doesn’t work precisely because of White’s inability to exploit the secondary defect induced by 1...Qxg6.