Figure 5.3.5.5[White to move]

Consider any threats White makes—always a sound inquiry at the start of a position. His queen attacks Black’s rook. The rook is defended by Black’s queen. A mission appears: drive off the Black queen. White has a bishop he can use for the purpose; he plays it to h3. In this case the queen has no place it can go that both is safe and allows it to keep protecting the rook on d8. It might seem that White therefore will win the rook easily, since after his 1. Bh3 the queen must move or be lost. But Black does have one other option: he can play f7-f6, interposing a pawn to block the path of White’s queen to his rook, and also threatening to take White’s queen with the pawn if White plays BxQ. When confronted with one of these threats—“if you take mine, I’ll take yours”—look at what each of you would be able to do on the board as it would appear after those captures have been made. What would you be able to attack once the pieces involved are on their new squares?

In this case White imagines playing BxQ and Black replying f6xQ. He pictures his bishop on d7 and asks what he would play, and the answer is clear: BxN, picking up not the guarded knight on e8 but rather the now-loose knight on a4. (When a bishop, or any piece, makes a capture, ask if it has any forking prospects in its new position.) This is yet another case where a queen protected two other pieces, creating eventual trouble for its owner.