Tries: 1.Sg1/g5? but 1…Bd7! 1.Qb6/c6/g6/h8? but 1…Rf6! Thematic Try: 1.Sf2? (thr. 2.Sd3#) but 1…Sxc4#! (Berlin theme). Key: 1.Qe6! (thr. 2.Qe5+ Sxe5/d4 3.Rgxd2#) Bxe6 2.Sf2 Sxc4+ 3.Ka6 Bc8+ 4.Ka7 any 5.Sd3# 2…Sb3+ 3.Kb6 Sc1 4.Sd3+ Kxb1 5.Rxc1#.
A problem showing the Berlin theme with a sacrificial key. In one variation, black's mate is turned into a harmless check; in the other check, the knight offer is refused and the black knight is allowed to provide an escape for the king. The white force obstructing the white king is bad.
