Now the same concept pushed out yet another step and seen from Black's side. Black is threatened with RxQ. The usual point repeats: don't retreat without considering how you might attack. The vague potential for a back rank mate exists because White’s king is stuck under its pawns without much protection except for its queen; the fantasy for Black is Qxf2 followed by mate on f1 or e1. White's queen stands in the way of this, so Black experiments with harassing moves like Re8 with either rook. Now if White plays RxQ, he gets mated with RxQ#. What else can White do?
(a) He doesn’t want to play QxR; he’ll then lose his queen on the recapture by Black's other rook, which renews the mate threat.
(b) If White moves his queen to d1, Black has checks: Qxf2, to which White must reply Kh1; then Re1+, to which White must reply QxR; then QxQ#.
(c) White can play Qf1, moving the queen out of the rook’s way but keeping it near enough to the king to provide protection. But now comes the pinning pattern we saw in the previous position. Black plays Qxf2+, taking the pawn in front of the king’s only guard and forcing the queen to recapture and become pinned; after White plays QxQ, Black has Re1#.
White’s best reply to Re8 was none of those moves; it was Qe3. This still results in losses, but it avoids the larger catastrophes that follow from the other moves. Play might go 1. …Re8; 2. Qe3, QxR; 3. NxQ, BxQ; 4. f2xB, and Black has won the exchange. Or Black might reply to Qe3 by moving his own queen over to b4. (Still another possibility is for White to reply to Re8 with Ne2. This blocks the e-file but leaves the rook on d5 loose and lets it be taken next move; it also leaves White with a bad position.)