Figure 4.2.4.8[White to move]

Again we find Black’s king and queen adjacent on the same diagonal with White’s queen pinning Black’s. White’s window of opportunity is small: he has one move to take offensive measures against Black’s queen or defensive measures to protect his own. Think offensively first. With one queen pinning another on a diagonal, a cross-pin against the target will have to be along a rank or file, which means it will have to be imposed by a rook. Does White have a way to bring a rook to bear against the pinned queen? Indeed: he already has a rook on the d-file. The only trouble is that White’s own bishop is in the way; this is a case where the cross-pin can be created not by moving a piece into position to attack but by moving a piece out of the way of an attacker.

So where should White move the bishop? Remember the purpose of the exercise: we’re trying to make it too costly for Black to play QxQ. Suppose the bishop is out of the picture and Black does play QxQ; with the bishop gone, White would then play RxR+—a check, but nothing more. It would become a familiar mating pattern, however, if the rook’s attack were supported by the bishop. White thus should play Be7. This not only discovers an attack on the queen by White’s rook, but also prepares the way (if Black plays QxQ) for RxR#. Black therefore can’t move his queen; the best he can do is NxB. White then has RxQ, winning the queen for a bishop and a rook.

Moving the bishop to e7 is a little counterintuitive because it looks like it can be taken so easily with QxB. Of course it can’t, since Black’s queen is pinned, but what the eye sees is that retreating the bishop to c5 or b4 looks safer and more appealing. To discipline yourself to consider possibilities such as Be7 it helps to very deliberately look at moves that put your pieces en prise to (exposed to capture by) the pinned piece. Such moves are easy for your opponent as well as for you to overlook.