Chess Opening Theory/1. d4/1...d5/2. e4/2...dxe4/3. Bc4/3...Nc6/4. Qh5

=Blackmar-Diemer Gambit (BDG)=

4. Qh5
White threatens to win a queen by checking on f7. Black should play g6 to stop the threat. However, if he, in his hotheaded desire plays Nf6??, Black faces doom with Qxf7+ Kd7 Be6+ Kd6 Bf4+ Ne5 Bxe5+ Kc6 Nc3 Bxe6 Qxe6+ Qd6 Bxd6.