Figure 6.2.13.4[Black to move]

Now let’s look at a couple of other things that might have happened in the position just considered. After White plays 2. Ng5+ (pictured), Black is not advised to retreat with Kg8; things are clogged on his back rank, so White then would have 3. Qh5 and a forced mate: 3. …BxN; 4. h4xB, f7-f5 (trying to create an escape route); 5. g5-g6 (sealing off f7), Qh4 (desperation—Black is out of ideas); 6. QxQ, anything; 7. Qh8# (with support from the rook on h1).

Another alternative for Black in the diagrammed position is BxN. This, too, results in mate: 3. h4xB+ (discovered check), Kg8; 4. Qh5, f7-f5 (this now looks like the sequence in the previous paragraph: Black can’t stop the threat on the h-file); 5. g5-g6 (again, see above), Qh4; 6. QxQ, anything; 7. Qh8#. Notice the crucial role played by the pawn that starts on h4. It provides protection for the knight; and when the knight gets taken the pawn turns into a monster, moving off the h-file to open it for the rook on h1 and then advancing up the g-file to seal in Black’s king. If that pawn isn’t there—if it’s on, say, h2 at the start of the position—then BxN is a sufficient response for Black here and ends the threat. Also crucial is White’s rook on h1. If it isn’t there (perhaps because White has castled), then h4xB no longer is a discovered check and Black has a chance to dig out of trouble.