Find the decisive blow (difficulty 1485)

87654321 abcdefgh

White to move

Show solution
87654321 abcdefgh
  1. e2–f3 key move
  2. b8–f8
  3. f3–e4

What makes it

The bishop strikes, a 4-point sacrifice, and the attack wins. No check, no capture: just a quiet move, and the defence caves in. 17 half-moves of forced play.