Find the decisive blow (difficulty 1530)

87654321 abcdefgh

White to move

Show solution
87654321 abcdefgh
  1. d1–h1 key move
  2. d2–e1
  3. h1–e1

What makes it

A rook move forces mate in 11. A quiet move, soft as anything, and yet there is no reply. 21 half-moves of forced play.