Chess Opening Theory/1. e4/1...e5/2. Nc3/2...d6/3. f4

White attacks e5 with the flanking f-pawn, hoping to prise the pawn away from control of the d4 square and then build a big centre with pawns on both d4 and e4. However, White has weakened their king and will have to play around that danger.

White plays in the manner of the Vienna gambit, but this is an inferior version. In the Vienna gambit, after 2...Nf6 3. f4, White can answer 3...exf4? with 4. e5!, kicking the knight back to g8, before defending their kingside with Nf3 and later recovering the pawn. White gets immediate compensation if the Vienna gambit is accepted, to the degree that 3...exf4? is considered a mistake.

However, in the Omaha gambit, there is no threat of e5, so 3...exf4 is critical. The resulting positions transpose into the Fischer defence to the king's gambit (1. e4 e5 2. f4 exf4 3. Nf3 d6), a line which includes ...d6 to prevent Ne5.

Alternatively, Black can ignore the gambit and allow White to take into them, 3...Nc6 4. fxe5 dxe5=.