Figure[White to move]

Now a study in caution. You see the obvious pin of Black’s knight on f6 by White’s bishop. It’s a relative pin, a theme we discuss later: Black’s knight can move legally, but his queen will be lost. Since the knight appears to be paralyzed as a defender, the Black pawn on d5 is free for the taking with Nxd5. If Black replies NxN, White seems able to play BxQ. Not so fast, however; this is a classic trap. When you imagine moving your pieces around, even just to make a capture, ask as a matter of course what lines the moves would open—especially when a piece like White’s knight starts out aligned with its king, so that moving it creates a new check for the other side. What checks would be possible for Black after White plays BxQ? Just one: Bb4+. The White king has no flight squares, so his only reply is to interpose his queen on d2. Black then plays BxQ, winning back the queen—and doing it with check, so that after White plays KxB Black still has a move to play KxB back at his end of the board, winning the bishop that took his queen. Black ends up with a piece in return for a pawn.