Tries: 1.b4? but 1…Bxc5! 1.c4+? (idea: 2.b4 or 2.Bb4; 1.c4+? bxc 2.b4? Bxc5!) but 1…bxc 2.Bb4 Qxf4! (2…Bxc5? 3.Rd2+!)
Solution: 1.Be3! Bxe3 2.Rd2+ Bxd2 3.b4 Qxe1+ 4.Kc2 Qc1+(b1+) 5.Rxc1(b1) Bxf4 6.Sxf8+ Ke5 7. Sd7# 5…Bxc3 6.Sg7+ Kd4 7.Sxf5#
Three pieces are sacrificed in the first three moves before the Siers battery fires, providing the two mates, one with an anticipatory self-block (5…Bxf4).
