Find the decisive blow (difficulty 1680)

87654321 abcdefgh

White to move

Show solution
87654321 abcdefgh
  1. h3–d3 key move
  2. g6–h5
  3. g5–f7

What makes it

A queen move and 5 points of material given up: mate in 11. The forced line runs 21 plies. Rated 1680 — punishing to calculate.