Walther von Holzhausen
White must threaten mate on the bottom rank, but 1...Rb2, creating room for the black king at a2, is the
tricky defence. If 1.Rg1, threat 2.Rg2+, 1...Rb2 leaves White in zugzwang (2.Rf1? Kd2 3.Rf2+ Ke1!).
The key is 1.Rf1, threat 2.Rf2+ K any 3.Rh1. If 1...Rb2 2.Rg1 places the rook out
of range of the king, with variations 2...Rb8+ 3.axb8Q and 4.Qh2 or 2...a2 3.Rg2+ Kb1 4.Rh1.
If 1...Kd2 2.Rf2+ Ke1 3.Rxa2 any 4.Rh1. A neat point is that the try 1.Rf3? Rb2 2.Rg3 fails because after
2...Rb8+ 3.axb8Q the queen cannot reach h2.