The studies so far in this chapter all have involved spotting a double attack waiting to be executed—and perhaps then perfecting it by loosening the forking square to make it available for the queen. Now we move to another pattern: the target piece—that is, the piece you intend to capture—does not start out loose; you have to loosen it with an exchange. Or it has to be moved onto a square where it is loose and can be forked. The thought process typically starts with the observation that your queen can check the enemy king; then, seeing no loose pieces it can attack at the same time, you get to work to create one.
We’ll start with a simple method. Look for checks your queen can give that also attack another enemy piece. If the piece is protected, ask whether you can capture it with one of your other men; perhaps when its replacement recaptures it will be left unprotected and will be a suitable target for a fork. Applying this approach to the position on the left, we find two queen checks to consider: Qe4 and Qf5. Ask whether you can attack anything else with those moves and you see that Qf5 threatens the Black bishop at d7. The bishop is an unsuitable target; it can hit back, and anyway it is protected. So ask whether White can take the bishop with another piece, forcing an exchange that will replace the bishop with a better target. He can: 1. RxB, NxR leaves a loose piece where there used to be a protected one. Now Qf5+ wins the knight, netting two minor pieces for a rook.
Another way to see this would be to start by examining captures you can make and their consequences. One capture for White to consider is RxB. You see that it provokes NxR. The critical step is to think about how the board would look after this exchange, asking what would then be possible. Note that the knight would be left loose and so would make a great target for a double attack. Might it be attacked with check? Yes, with Qf5+.