Figure[White to move]

The pattern here is structurally the same as the others just seen in this chapter but looks a little different. The initial cue is that the two queens are faced off against each other. If one becomes loose, the other takes it. Although Black’s queen seems surrounded by pieces, in fact it is guarded only by its king and thus is highly vulnerable. The next thought is to check the king and force it to move despite its apparent insulation. Surveying his pieces, White does find one check usable for the purpose: his bishop can take Black’s f7 pawn. Indeed, Bxf7+ is a classic sacrifice to force the king to move; f7 often is a weak square before a king castles—“weak” because only the king protects it. In reply Black’s only legal move is KxB. Now White plays QxQ, winning a queen and pawn for his bishop.