As you no doubt are noticing, the tools required to create bishop forks are the same used to create many forks by the queen and some by the knight. Here, as in those other cases, there often may be a forking square that needs to be loosened; the techniques for loosening it—e.g., a preliminary capture of the piece that currently sits on the square, or of the guardian of it—are the same regardless of whether the goal is to put a bishop, queen, or knight on the square. It would be possible just to leave it at that, but for the sake of building pattern recognition skills it will be worthwhile to see at least a few examples of how these processes look in the context of double attacks by the bishop.
And in any event the thought process is not quite the same. In this section we consider cases where the bishop has no way to give a check, but where with some work you can build a fork that involves an attack on the enemy king at one end. The crucial initial question is how you would realize there is an opportunity for such fork-building in the first place. If the bishop has no checks, what would cause you to try to create a fork involving one? The answer, of course, is that you look for any other pieces the bishop can threaten that would form good targets for a double attack; having found one, you then go to work to create a check at the other end. We saw that in the queen’s case this generally meant that you had to find or create a loose piece to attack, because a queen can’t afford to attack anything that is protected. One of the pleasures of attacking with the bishop, however, is that its list of good targets is longer; thus these positions require you to start by considering carefully whether the bishop can threaten any loose pieces, or rooks, or queens.
These problems may require you to keep developing some new habits. If you are not an experienced player you probably are accustomed to asking what pieces your bishop (or your other pieces) can capture on the next move, but not what pieces your bishop can threaten on the next move (and thus capture in two moves). But that is the important question here, as it often was in the earlier chapters. In the bishop’s case the examination of possible threats is pretty easy because the movements the piece makes are limited and easy to follow. It also simplifies the task to remember that any possible targets of the bishop must sit on the same color square that it does.
The visual patterns we used to set the analytical process in motion in the last section may be a little less helpful here, because at the beginning of these positions the king and the target piece tend not to be on the same diagonal or triangle. You still may be able to see that the king almost is aligned with another piece, and so have the idea of moving them into alignment with each other. Even if you don’t see that, the key patterns emerge here after an initial exchange or two; and much the point of mastering the relevant visual patterns is to be able to recognize them not just at the beginning of a position but as they emerge after you have imagined initial forcing moves and responses in your mind’s eye.
Turning to the position on the left: What Black pieces can White’s bishop attack? (We do not just ask what Black pieces are loose, because a more valuable enemy piece may be a good target for a bishop even if it is protected.) Answer: it can attack the rook by moving to d2 or d4. Threatening a rook is a nice start, but becomes really interesting only if it also is accompanied by another threat in a different direction—i.e., if it is part of a fork. So what other threat can be engineered into existence? Bd4 aims the bishop in the king’s general direction; if the king could be moved onto the same diagonal as the rook, White would have a double attack. What checks does White have that force the king to move? Only one: f4-f5+. Carefully consider Black’s options in response. He can move the king to e5 or f6; there is nothing else. Either move puts the king into the path of the White bishop once it moves to d4+; and after the king then moves again, BxR takes the rook. Black can recapture with his other rook, but White wins the exchange.