Find the decisive blow (difficulty 1590)

87654321 abcdefgh

White to move

Show solution
87654321 abcdefgh
  1. a2–b3 key move
  2. f6–e5
  3. f1–c4

What makes it

The pawn strikes, a queen given up, and the attack wins. It calculates 22 plies deep. At 1590, punishing to calculate.