Opponent Blunders

The blunders of my opponent in a game of speed chess enabled me to mate in 18 moves.  My opponent who played black was Dragstar of Serbia.  Here are the moves of the game along with my commentary:

1. e4 e5
2. Nf3 Nf6
3. Nxe5 Qe7

Black usually plays d6 here.

4. d4 d6
5. Nc4 b5

Black attacks my knight again, but this pawn move is committal.  It is better to regain material equality with Nxe4.

6. Ncd2 Bg4

Black makes a bad move.  Now I can attack the black bishop and protect my e-pawn on my next move.  The move Nxe4 is better.

7. f3 Bd7

Now black cannot capture the e-pawn.

8. Bd3 Nc6
9. c3 a6
10. 0-0 Nh5
11. Nb3 g5
12. f4 gxf

The black knight is unprotected.  A better move is Nf6.

13. Qxh5 0-0-0
14. Bxf4 h6
15. a4 bxa

With the black queenside already quite exposed, black must not allow me to open the position more.  A better move for black is Na7.

16. Bxa6+ Kb8

The black king has inadequate protection.  Now black cannot prevent mate.

17. Qb5+ Ka7
18. Qb7#

Black makes two blunders in this game.  The first blunder is gxf on the twelfth move, a move which leads to the loss of the knight on h5.  The second blunder is on the fifteenth move, bxa, which exposes the king to a decisive attack.  Both blunders in this game are captures.  This game illustrates that captures are sometimes inferior moves.