Find the decisive blow (difficulty 1125)

87654321 abcdefgh

White to move

Show solution
87654321 abcdefgh
  1. e3–e4 key move
  2. f6–b2
  3. b1–b2

What makes it

It starts with a queen move and forces mate in five. A quiet move, soft as anything, and yet there is no reply. It calculates 9 plies deep.