In our earlier studies of various tactical themes we often saw them combined with back rank mates: queen forks or discovered attacks, for example, in which a loose piece and a mating square on the back rank were the two targets threatened at once. But it still will help round out our consideration of back rank mates to reconsider those ways that the concepts studied here can be put together with the concepts we have examined elsewhere.
Some general points: think of back rank patterns not just as ways to mate but as ways to threaten mate that can be combined with other threats to create double attacks. The clues to look for are a king stuck behind its pawns or otherwise trapped, an absence or shortage of defenders on the back rank, and a piece you can aim there—perhaps as part of a battery with a piece already so aimed. When these indications are present, there are a few ways they can contribute to forks even if the mating idea itself fails:
a. A piece tied down to guard duty on the back rank may be unable to guard other squares within its reach—squares from which you can launch forks.
b. If there is an enemy piece preventing the back rank mate from succeeding, it might itself make a good target for one end of a fork, just as a loose or pinned piece would.
c. If the mating idea fails because your pieces get taken when they reach the back rank, it sometimes may be possible to inflict a fork at the end of the sequence against pieces that have been left loose there.
d. Sometimes you will have no threat against the back rank but you can make one, perhaps by moving your queen to an open file that leads there. Of course this gives your opponent a move he can spend defusing the threat. But the time he spends doing this gives you a move to use capturing something else. In other words, a back rank mate can be just another mating threat at one end of a fork—usually a queen fork.
In the example to the left White has an aggressively placed knight, and a look at its moves turns up a fork of Black’s king and queen with 1. Nf7. The fork seems to fail because f7 is protected by Black’s rook, but then you play through Black’s capture RxN and see that it removes the rook from the back rank, leaving Black’s king bereft of defenders there. So analyze the follow-up—and be careful. The move of White’s knight will have opened the e-file for the natural Re8+. It would be easy to imagine that Black now plays Rf8, a useless interposition that gives White RxR# (or that Black plays Bf8 with the same result). Not quite, however, for f8 will be guarded both by Black’s bishop and by the rook then on f7.
All this need not dissuade you; it only should cause you to build backwards and start by taking out Black’s bishop with 1. QxB, c7xQ. Now comes the knight fork Nf7+, where Black must forfeit his queen or play RxN and be mated a move later. Assuming he lets go of the queen, White nets a piece with the sequence (the bishop he took at the outset)—and of course this is better than just winning the exchange with 1. Nf7+, RxN; 2. BxR.
At bottom this is an example of motif (a) described above. The rook on f8 turns out to be overworked; its responsibilities on the back rank prevent it from guarding f7, which serves as a forking square for White.