This time Black has moved one of the pawns in front of his king, but White compensates with an attack by his bishop on h7. Black’s king thus remains trapped on its back rank, and again there are no heavy pieces on the rank to defend it. An empty back rank invites thoughts of mate even without a battery, as we just saw; a single rook may do the job. White can’t play Rd8+ because the square is protected by Black’s queen, but what about playing the other rook to a8? Now Black’s only defenses are interpositions, so walk through them. He can play his queen to d8, but White takes it with either of his rooks; then Black can put his bishop on e8, but again White takes it and mates. So Black’s interpositions are useless and the sequence works.