Chess Opening Theory/1. f4/1...e5/2. fxe5/2...d6/3. exd6

3.exd6
After this, Black's only sensible move is Bxd6, developing with a threat. However, Nf6, the Langheld Gambit has also been tried with similar ideas to the mainline but with a Queen on c7 instead of a pawn.