Vienna Gambit

After 2...Nf6, the advance 3.f4 carries out the original purpose of the Vienna Game: a King's Gambit with the queen's knight already developed. White attacks e5 at once, aiming to open the f-file and, if Black captures, to gain time by pushing e4-e5 against the knight on f6. The usual follow-up involves Nf3 and Bc4, with pressure against the center and the black kingside. The name originally belonged to 2...Nc6 3.f4; in online usage it now refers mainly to this position.

Accepting with 3...exf4 is the most frequent reply in practice but the least respected. After 4.e5 the f6-knight has almost nowhere to go and normally returns to g8, and White can later regain the f4-pawn with a broad center and a lead in development; White's results against the capture are especially good. The sound alternative 3...d6 shores up e5 and steers the game into King's Gambit Declined territory. A known problem for Black there is 4.Nf3 Nc6 5.Bb5 Bd7 6.d3, when the threat to remove the c6-knight and win e5 pushes Black into 6...exf4 7.Bxf4, leaving White comfortable. The developing move 3...Nc6 is considered weak because of 4.fxe5 Nxe5 5.d4 and a quick e4-e5.

The principal answer is the central counterstrike 3...d5, in the spirit of the Falkbeer Countergambit. After 4.fxe5 Nxe4 Black's knight stands actively in the center while White has the e5-pawn and the half-open f-file. The traditional 5.Nf3 is met chiefly by 5...Be7, the Breyer Variation, or by 5...Bg4 6.Qe2, the Kaufmann Variation. In the Breyer, play often runs 6.Qe2 Nxc3 7.dxc3, with White castling long and pushing the h-pawn while Black counters on the queenside with ...c5 and ...Qa5. The Paulsen Attack, 5.Qf3, puts the queen on an aggressive square at once; 5...f5 is the Bardeleben Variation. The Modern Variation, 5.d3, questions the knight immediately, and the greedy 5...Qh4+ 6.g3 Nxg3 7.Nf3 Qh5 8.Nxd5 is the Würzburger Trap. White can also avoid 4.fxe5 with the Steinitz Variation, 4.d3, or with 4.exd5, which can transpose into King's Gambit lines.

The gambit was popular in the 19th century and was later advocated by Anthony Santasiere and Weaver W. Adams, while Raymond Keene judged it too risky for grandmaster play. It has regained popularity in recent years, helped by IM Levy Rozman's regular use of it in online content. The engine regards the position as roughly balanced, yet White's practical results in online play are strong, reflecting how easily Black can go wrong in the sharp positions that arise.