Figure[White to move]

A similar idea. First find where White has the makings of a discovered attack. The kernel lies on the long a1-h8 diagonal, where White’s rook masks his queen in familiar fashion. Look for a target for the queen once it’s unmasked and see that Black’s queen is in the line of fire—and that it's loose. The challenge now is straightforward: vacate the rook from d4 in a way that compels a response from Black. The rook has no checks, so examine the Black king’s position for vulnerabilities. It is trapped on the back rank; although it isn’t entirely sealed in by its pawns, White’s bishop closes off the flight square on g7. The same idea we saw in the previous position thus works here. An attack by White’s rook against Black’s rook on e8 would be a mating threat, because if White can play RxR the game ends. White makes the threat with Re4. Black has to eliminate White’s rook to stay in the game. He has two ways to do it. The first is BxR, to which White replies QxQ and mates soon. Black also has the option of replying to Re4 with RxR. How should White reply?

This time the answer for White isn't quite QxQ, since Black then uses his rook to mate on e1. White instead needs to work with checks to prevent that possibility. By moving his rook off the back rank, Black has made this easy: White plays Qc8+, which requires Black to interpose his queen on d8. White takes it (QxQ+); then we go through the same process with Black's rook; then it's mate.

Black's best reply to 1. Re4 is probably 1. ...Qe5, which avoids the mate just shown but loses his queen and then his bishop.