Jörg Kuhlmann & BDS
The Problemist, 2000
R#2
KöKo
1.Rb6! (2.Rh1 g1=Q,g1=R#) 1...Rxh4 2.Qh7 Qg6# 1...Bf1 2.Rb8 Rb7#
The key, taking the flight at c2 from the white king, is very strong. 1...Rxh4 opens the white queen’s guard of g1, but removes White’s guard of g6, so allowing the critical move 2.Qh7, followed by 2...Qg6#. 1...Bf1 blocks the threatened line of mate, but removes a piece adjacent to b7, allowing another critical move 2.Rb8, followed by 2...Rb7#.
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