Figure 5.3.6.3[White to move]

Now vary the elements a bit more, yet see how they are functionally unchanged. It starts with the simple point that White has a capture in RxR but that Black’s queen protects the rook. But RxR also would be a check of Black’s king. This means White would have the priority of check on his side and so can take some risks that might otherwise lead to losses; he may be able to make two captures in a row. He therefore can afford to threaten Black’s queen with his own, and allow his queen to be captured, because then he will be able to take the rook (with check) and Black’s queen on successive moves. So he looks for a square from which he can attack Black’s queen with protection, and finds Qg4+. The move is a check, which matters: White has forked Black’s king and queen. Black must address the threat to his king, but if he merely moves it out of the way he loses his queen next move. He therefore plays QxQ. Now White takes his two moves: RxR+; and then, when the king moves to g7, f3xQ. White nets a rook.