Black has some pieces poised for action against the White king’s area, but the king seems safe enough because it is protected by its queen and because Black can’t quite coordinate his pieces to deliver mate. Again, before the idea can emerge you probably will need to experiment with Black’s possible checks. There is only one: QxQ, to which White must reply KxQ. The exchange of queens leaves White’s king a little more exposed, but Black’s rook is on the wrong file to be able to deliver a classic rook-and-bishop mate at e1. Still, examine Black’s checks in this resulting position and again there is just one: Rd1+. This forces White’s king up onto the second rank, onto e2—and into line with his rook, which is loose. Now the idea is clear; the checks have forced an alignment of White’s pieces, perhaps unexpectedly. This calls for a skewer. Black now is able to get mileage after all from that bishop on b4, as it allows his next and final check: Re1+, moving the rook next to the king with protection. The king moves, and now comes RxR, winning a rook.

When you push the enemy king around, be mindful of skewering possibilities in every direction—vertical, horizontal, and diagonal.