Find the Move #17

31. Rxb6#

Morphy's mate. The king has just taken the knight on d5. But the rook takes the pawn on b6, and that opens the diagonal for the bishop on b7: a discovered check. The rook covers c6 and d6, the pawn on d4 covers c5 and e5, and White's own king on d3 covers c4 and e4. The pawn on d4 can't be taken, because it is protected, and Black's own bishop stands on e6.