Figure 3.3.4.7[White to move]

Notice the kernel of a discovery in the White knight’s masking of his queen; see how White’s two knights both are within a move of bearing down on the king’s general position; observe that the king’s position is cramped. The main structural difference lies in the target: if the f4 knight moves, White only has a bishop to attack with his unmasked queen. But the bishop already is attacked once and protected once, so it’s a perfect occasion for a preliminary exchange: 1. RxB, and then if Black recaptures QxR, the pattern is much like the one in the previous frame. 2. Ng6 cuts off the Black king’s only escape square, allowing White to threaten mate with Nd5-e7; so after Ng6 Black can’t play QxQ. He has to protect his king with a move like h7xN, and then White is the one who plays QxQ.

In a sequence like this you have to ask whether the attacked Black queen might have some way to both remove itself from danger and defuse the mating threat by perhaps taking one of the pieces involved in it. That wasn’t a problem in the previous position because the pieces contributing to the mate threat had protection. But here Black could reply to White’s 2. Ng6 with QxNd5, eliminating both the threat of QxQ and the mating threat of Nd5-e7. Yet after noticing such a capture consider (our mantra) the next check you would be able to play. There would be two here for White: Qxh7+, which would not work very well, and 2. Ng6-e7, which would work very well indeed—not only because it forks Black’s king and queen (always think about forks when you move your knight), but because after the compulsory 2. …Kh8 White blows open the h-file and mates there with 3. Qxh7+, KxQ, 4. Rh1+, Qh5, 5. RxQ#.

This sequence might look a little long, but notice that White can foresee the whole thing by simply asking what checks he would have after each of Black’s evasive maneuvers: there never are more than two for him to worry about here, and eventually they lead to mate. The trick is to remember all of your potential checking resources—including the rooks on your back rank, which can be moved to the h-file in a hurry. We will look more closely at this idea in the section on classic mating patterns.