Figure[Black to move]

Now a reminder that a discovered mate threat can be formidable, too. The alignment of pieces on the d1-h5 diagonal cries out for consideration of a discovered attack; if Black moves his rook from e2, his queen will threaten not only to take White’s rook on d1 but to mate there—almost; White’s queen presently guards the square. The question for Black is the best use he might make of his rook as it unmasks the threat, and the natural answer is to go after the White queen that protects the rook. He experiments with Rb2. If White plays the capture QxR, Black mates as just noted. Nor can White move his queen to any other square where it will prevent mate. The best he can do is Qxd5, taking a pawn and guarding against immediate mate by protecting the d1 square. But then Black takes the queen with his c6 pawn (or with his own queen—it doesn’t matter) and White has nothing left but Rf1. Black is ahead by a queen and has a won game.

The discovered attack here seemed at first to be foiled by White’s queen, which appeared to guard the targeted piece. Consider in such a case whether the discovered attack might be turned against the very piece that seems to frustrate it.