Figure[White to move]

The current principle can be used by the queen without a bishop. Here White sees the coordination of his queen and rook against f7, and so experiments with attacks by his queen: the check 1. Qxf7 forces Kh8, since the queen has protection; and now that Black’s king has been forced into the corner it no longer will be able to defend itself. The resulting position has two heavy White pieces trained on the mating square f8 and just one Black piece—his rook—available for defense. Thus 2. Qf8+, RxQ; 3. RxR#.