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Solution: An immediate check on b8 fails to the cross-check, but White can exploit the fact that Black must
maintain this defence by playing a subtle critical move 1.Rd7, which prepares a pin. After
1...Qg5 2.Qb8+ Rd6+ 3.Bxg5 Kd4 White finishes with a switchback mate 4.Qh8.
Peter Niehoff: White - Black Indian with switchback of the white queen.
Dafydd Johnston: This is a fine example of the pleasure to be had from the solving process. 1. Qb8 fails to 1...Rd6 with discovered check, but at first sight it looks as if a random rook move on the d-file, e.g. 1. Rd3, will force Black to abandon the queen battery. However, Black has the resource 1...Qg5 since capturing the queen gives stalemate. So the white rook must cross the critical square d6 with 1. Rd7. After 1...Qg5 White plays 2. Qb8+ Rd6+ and can then safely capture the queen with 3. Bxg5 because the Black king now has a flight on d4. And then comes the surprise switchback 4. Qh8 mate, the black rook being pinned on the d-file, having previously been pinned by the queen on two different diagonals. The two bishops cut off the king's escape and now we see the reason for the pawns on b3, c4 and c5. Lovely construction and line-play.
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