Figure[White to move]

This time start by looking for pairs of Black pieces that might be vulnerable to a bishop fork. How? Look for pieces on squares of the same color, or on the same or intersecting diagonals. The c5 knight and e7 bishop are in the right pattern, but there is no way to exchange the bishop for a suitable target. But now what about the pieces on light squares? Black’s rooks are on a6 and a8—on the same file, one square apart, and arranged for a bishop fork with Bxb7. White’s light-squared bishop is aimed the right way; the only trouble is that White’s own pawn is in the way at d5. If it is going to move, first the Black pawn in front of it has to be moved. You move a pawn by capturing something it protects; here it protects the knight at c5, so 1. NxN (capture with the least valuable piece you can), leading to 1. …d6xN, clears Black’s d-pawn onto the c-file. Now White moves his own pawn forward to d6, making a threat against Black’s bishop that requires a time-consuming response. After the bishop moves (presumably with Bxd6), White is able to play Bxb7, forking both Black rooks and winning the exchange next move.