Figure[White to move]

Here is a study in temptation best resisted. Black’s bishop on g4 is loose; so is his knight on c3—and it’s under attack. Should White play QxN? So it seems, since Black has no way to recapture. But worry not just about whether your capture results in a recapture but also about whether it creates any patterns that you or your opponent would be able to exploit. An important example is the capture that leaves one of your pieces in position to be forked; another, relevant here, is the capture that leaves one of your pieces aligned with your king, and so able to be pinned. Thus the key fact about QxN for White is that it puts his queen in line with his king with nothing between them. Would Black be able to take advantage? Yes: his dark-squared bishop is available to play Bb4—and since that square is guarded by Black’s queen, White wouldn't be able to escape trouble by striking back with QxB. He would lose his queen. So the initial capture QxN is unsafe.