The Halosar Trap is a variation in the Blackmar-Diemer Gambit. A natural looking pin that apparently prevents white from castling by promising to win the exchange proves to be inferior, as white has a nice combination to threaten mate and gain a huge lead in development and position Its most common move order is:

1. d4 d5
2. e4 dxe4
3. Nc3 Nf6
4. f3 exf3
5. Qxf3 Qxd4
6. Be3 Qb4?!
7. 0-0-0 Bg4?
8. Nb5!!

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