What visual pattern do you see? Black’s king and knight on the same diagonal; this suggests that conditions may be right for a fork. Bd5+ almost does it, but the rook at d3 protects both the forking square and the targeted knight. White can’t capture the rook, so he proceeds by asking if he might capture the knight with some other piece, thus attracting the rook onto the knight’s square when it recaptures and leaving it loose. He can. 1. RxN, RxR both loosens the forking square and creates a loose target. Now Bd5+ forks and wins the rook.