Figure 5.3.8.4[White to move]

Now back to another family of mating patterns we frequently consider: the tightly constrained king. White’s e4 bishop is threatened by the pawn on f5, but of course you decline to retreat until you have studied your attacking options. Examine the Black king’s position and you see that it has no flight squares; it is frozen on g8, with an open diagonal leading toward it. Consider this an invitation to put an attacker on that diagonal, since the king won't be able to run away from it. Does White have a piece usable for the purpose? He could try Bd5+, but Black has the square protected with his rook as well as his queen. So White tries his other resource for attacking on a diagonal: his queen, which he might play to c4. This fails because, again, Black guards c4 with his queen. So the next thought is to put pressure on Black’s queen, and one way to do this is by putting one of your pieces flush against it—as with Ra1. Black’s goal now is familiar. Can he move his queen someplace where it (a) is safe and (b) still protects the mating square c4? No. The a-file is off limits, and the queen has no safe squares on the light-squared diagonal it is trying to protect.

So perhaps it appears that Ra1 ends the game. Not quite, however; there is another line of response for Black: he can attack White’s queen with Nd4. It’s a familiar defensive idea: if you can’t stop your opponent's attack on one of your pieces, make a similar attack on one of his pieces. White isn’t fazed by this, though, as he has a couple of fine options in reply.

(a) He can go ahead and trade queens with 2. RxQ, NxQ. A few positions ago we saw a similar situation and emphasized the importance of not assuming that you should liquidate in this way. That was true: you shouldn’t assume it. It depends on what the board looks like before and after such a liquidation occurs. Here, after 1. Ra1, Nd4; 2. RxQ, NxQ, White now has attacks against two loose pieces: Black’s knight, which sits loose next to White’s king, and Black’s bishop, which is loose on b7. So White wins a piece with 3. BxB. (And then a pawn, too, after 3. …Nd4, 4. Rxa7.)

(b) Or White could reply to 1. …Nd4 with 2. BxN. Now he has a piece; and if Black plays 2. …QxR, trying to win the exchange, White has 3. Qc4+—and mates soon thereafter. The resulting position is shown in the next frame.