Key: 1.Sf8 Bxf8 2.Qf2 gxf2 3.exd4 cxd4+ 4.c5 Bxc5+ 5.Kb2 a3+ 6.Kxb3 any 7.Bf4+ Bd6 8.Bxd6# 5…Bd6 6.Sxd6 a3+ 7.Kxb3 any 8.Rh8#
Extended Berlin.
A double sacrificial moremover showing a delayed Berlin theme. Both sacrifices are designed to effect clearance for the white pieces; the key clears the way for the white rook and diverts the black bishop from the b8-h2 diagonal. The knight must be sacrificed first, 1.Qf2? Ra6! - black has time to free himself as there is no danger on the diagonal.
Following the knight sacrifice, the Berlin mechanism is shown 2.Qf2! sacrifices the white queen for a pawn now one square from promotion, whereas 2.exd (White's main plan or Hauptplan) leads to mate 2...cxd4+ 3.c5 Bxc5#. This sacrifice reduces the mate to a harmless check, allowing white to carry out his plan to mate with Bf4 or with a corner-to-corner (h1-h8) maneuver of the white rook. The other sacrificial clearance moves 2.Qh2? 2.Qg2? fail as the white rook file is then blocked or the white rook threatened.
