Vienna Gambit, Main Line

The Main Line of the Vienna Gambit arises when Black meets 3. f4 with 3...d5, borrowing the idea of the Falkbeer Countergambit. Black neither defends e5 nor takes the f-pawn. Instead Black opens the center while White's king is still uncastled and the e4-pawn is attacked by both the knight and the d-pawn. White leaves the main line rarely: 4. fxe5 is chosen in nearly four games out of five. After 4...Nxe4 the knight stands actively in the center, and play branches into 5. Nf3, 5. Qf3 and 5. d3.

The alternatives are much less common. 4. exd5 is the most notable of them. After 4...exf4 5. Nf3 it transposes to the Modern Defense of the King's Gambit Accepted, while 4...e4 reaches the old main line of the Falkbeer Countergambit. The Steinitz Variation, 4. d3, aims to hold the center but tends to hand Black the initiative. Recapturing on e4 with the d-pawn allows a queen exchange on d1 that strips White of castling. 4. Nf3 is also seen occasionally. The engine judges the position roughly balanced, and online results are close to even, with White slightly ahead.