Black has opened up h7, but once more White closes it down with his d3 bishop. Again White looks for ways to take advantage of the king’s trapped position and sees that he has a rook and queen at the ready. Black’s bishop guards c8 against occupation by White’s queen and also blocks the path of White’s rook to e8, but when you see these two functions the bishop serves you realize it is stretched too thin. White thus distracts the bishop away by beginning with the queen: 1. QxR+, BxQ; 2. Re8#. It's an example of how a guard of the back rank can be overworked, a theme we will study in more detail later. It also is an example of the usefulness of directing a bishop against h7 when the square is open in the way we see here. Among other things such an attack may lay groundwork for a back rank mate.