We now consider a common pattern that is a variation on the theme just considered. Often a possible bishop fork has a pair of problems: the piece it would target is protected, and the piece also guards the forking square. This most frequently happens when the target of the potential fork is a bishop or pawn. The solution then is to perform an exchange with one of your other pieces that trades the bishop or pawn for a better target—one that is loose and that cannot fire back at your own bishop when it executes the fork.

An illustration will make the point clearer. Recall our current drill: look for any enemy pieces lined up on the same diagonal, and especially for pieces lined up on the same diagonal as the king. Here Black’s king and bishop are aligned. The bishop won’t work as a target for a bishop fork; it is protected and it can attack the forking square. But seeing the geometry still can provide an idea to motivate your examination of forcing moves. A common way to deal with an unsuitable target is by capturing it with another piece, allowing a recapture, and then executing the fork against its replacement. So the solution here is the preliminary exchange RxB. If Black responds with RxR, now the bishop has been replaced with a rook that is loose and that cannot guard the forking square. Bc5+ wins back the rook and nets a bishop.