Chess Opening Theory/1. d4/1...d5/2. e4

= Blackmar-Diemer Gambit 2. e4 =

2. e4
White offers their e4 pawn in exchange for quick development and open lines. At the professional level this move is considered somewhat suspect, but Black must be careful if they choose to take the pawn as there are many traps in this opening. 2 ...dxe4, accepting the pawn, is the Blackmar-Diemer Gambit. Black has three ways to decline the gambit.
 * e6 transposes to the French Defence
 * c6 transposes to the Caro-Kann Defence
 * Nc6 transposes to the Nimzowitsch Defence
 * c5 is a largely unexplored countergambit.

Theory table
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'''1. d4 d5 2. e4'''