Figure 3.3.9.5[Black to move]

Black has the kernel of a discovery leading toward White’s king on h3-g2. He could use his knight to go hunting for White's queen, but the idea is complicated by the attack underway against his own queen; and in any event, when the king’s position is so cramped it makes sense to focus on the possibility of mate. If Black's knight moves, White’s only option is to move his king to e1 or g1. Imagine the knight out of the way—moved to h4—and consider how it could go after the king on either of those flight squares.

(a) If White plays Ke1, what checks does Black then have? QxB, which doesn’t work; and NxN, which is mate because the bishop on e2 is pinned.

(b) If White instead plays Kg1, NxN no longer works because BxN results, the bishop not being subject to a pin. But this time the queen check does work: Qg4# ends the game.

This is a good study in the value of carefully examining the checks you can give at every turn. After Black's first move the White king has two places to go. Either way, Black has two checks; and either way, one of them is ineffectual while the other is mate.