The next point to grasp is that the pattern just shown can be forced once you reach the position shown here. White moves his pawn to f6, and this threatens Qxg7#; Black has no choice but to advance his g-pawn to g6. Now White plays Qh6 and mates with Qg7 next move. As we have seen, this is a common way to force a pawn in front of the enemy king to step forward: if you threaten to mate by capturing it, you may force it to advance so it will be protected by its fellows and not just by its king. This has the side effect of opening a diagonal line to the king’s position that can be exploited in many different ways. Here we see another.