Blackmar-Diemer Gambit, Halosar Trap

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Black falls into the trap with 7...Bg4??

The Halosar Trap (named after Hermann Halosar) is a chess opening trap in the Blackmar-Diemer Gambit.

Analysis

1. d4 d5 2. e4?!

This is the start of the Blackmar-Diemer Gambit.

2... dxe4 3. Nc3 Nf6 4. f3 exf3

Now 5.Nxf3 is usual, but by capturing with the queen, White lays a trap. (This is the Ryder Gambit.)

5. Qxf3?! Qxd4 6. Be3 Qb4?!

Better is 6...Qg4. Black thinks that castling is prevented because of ...Bg4, but White castles anyway.

7. 0-0-0 Bg4?? (see diagram)

Blundering into the trap.

8. Nb5!!

White threatens mate with 9.Nxc7#. The black queen cannot capture the knight because 8...Qxb5 9.Bxb5+ is check, gaining time for the white queen to escape the black Bg4's attack.

8... Na6 9. Qxb7 Qe4

Black lost even more quickly in Diemer-Halosar, Baden-Baden 1934, after 9...Rc8 10.Qxa6 1-0.

10. Qxa6 Qxe3+

Worse is 10...Bxd1 11.Kxd1 Rd8+ 12.Bd2 and White is winning, for example 12...Ng4 13.Nxc7+ Kd7 14.Qxa7.

11. Kb1 Qc5 (diagram)

	a	b	c	d	e	f	g	h
8									8
7									7
6									6
5									5
4									4
3									3
2									2
1									1
	a	b	c	d	e	f	g	h

Position after 11...Qc5

12. Nf3

The White threat of 13.Qb7 wins the black a-pawn by force. With even material and a passed a-pawn, White will have a winning advantage (Burgess). Even stronger seems 12.Qb7! with the idea 12...Bxd1 13.Qxa8+ Kd7 14.Nc3 and White has a winning attack.