Figure[White to move]

A difficulty in using our current mating pattern is that if Black has a pawn on h7, then g6 probably isn’t safe for your knight; but if Black doesn’t have a pawn on h7, then his king can move there and perhaps escape the mate. We have seen three ways to deal with this: make a sacrifice on h7 that causes the pawn to be replaced by a piece that can’t defend g6; pin the pawn with a rook; or, if the pawn has been moved forward, set up an attack against h7 with another piece so that you will have a discovered check if the enemy king moves there. Here is a final method. You see that White controls g8 with his bishop, so your thoughts turn to ways of pressuring h8. The natural idea is NxN+, which would work except that Black has a pawn on h7 and so can reply h7xN. Well, but what if he does? The capture leaves open Black’s end of the h-file, so White will mate if he can rush a heavy piece there; and he can, with Qh3#—Greco’s mate after all. Thus the pattern of the current mate is used to pry open the h-file, which turns out to have other happy consequences.