Figure 2.3.5.2[White to move]

What Black pieces can White’s bishops attack? (Not what can they capture, but what can they threaten by moving.) Bf5 attacks the rook at e4. (The other rook is loose, but the dark-squared bishop can’t reach any squares from which to attack it.) The light-squared bishop would have a fork if Black’s king somehow could be moved onto g6. The simplest way to move the king is with checks, and White has two. The first is Rf5, but this will not necessarily achieve the desired end (Black can play Kh6 or Kg6; Kg6 sets up a fork, but White can’t pull the trigger because his own rook is then on the square that his bishop needs). White’s other check is Bc1+—another study in the importance of remembering backward moves. Black would have to either move the king to g6, thus walking into the fork Bf5+ and losing the rook; or he could try his only interposition: Re3, blocking the check. But then White plays BxR and wins the exchange. So 1. Bc1+ wins regardless. White starts out ahead in that he has two pieces for Black’s rook; after winning the exchange he is ahead by a whole piece.