Figure[White to move]

This example combines two recent points we have studied. The initial key is to see the potential knight fork Nd5 despite the fact that you already occupy d5 with another piece. The question is how best to vacate the bishop from the forking square. It runs on the light squares and the king is on a dark one, so the bishop won’t be able to deliver a check. Is there anything that it might capture? Yes: Black’s bishop. But before you play BxB, notice (as would be obvious in a game) that Black is about to play QxQ, ruining your fun. So the correct play goes 1. QxQ, RxQ; then 2. BxB, b5xB; 3. Nd5, forking the rooks.

This position, like the previous one, contains a rook that looks unassuming but that provides crucial support for the whole sequence: the one on f1. Imagine it gone and rethink the position. Now in reply to 3. Nd5, Black moves his rook from e7 to d7; and if White then plays the capture NxRf6, Black has RxRd1+. (In effect Black uses his rook to pin the White knight to the White rook on d1.) In the actual position White’s rook on f1 prevents this because it protects the rook on d1. The general lesson you can draw from this little note is that loose pieces (as the d1 rook would be if the f1 rook were gone) are a hazard. Even if they don’t appear to be part of the action, they can find themselves suddenly captured during or after a sequence you are planning elsewhere.