Checkmate Exercises

After losing a tense and interesting struggle in round four, my fifth round opponent in the Eastern Washington Open perceived an attack where none existed and lost a piece. Soon, my pieces were aiming at his king.

White to move

18.f6

I knew this move led to checkmate in a few moves.

18...g6

From here I calculated the moves all the way to checkmate, but my calculation was incorrect.

18...Qxf6 offers the most stubborn defense. 19.exf6 e5

White to move

Analysis diagram

What sequence forces checkmate in six?

19.Qf4 Kh8 20.Qh6 Rg8

White to move

21.Rf3?!

This inaccuracy allows Black to hold out a couple of moves longer. What was the correct move?

21...Qf8

Now I have a mate in three.

White to move

What was my next move? It provoked resignation.

Had Black played 21...Qxf6, the move that exploits my inaccuracy, what would be my quickest mating sequence?

White to move

Analysis diagram