Falkbeer Variation

The Falkbeer Variation, named after Ernst Falkbeer, answers 2. Nc3 by developing the king's knight with immediate pressure on e4 and a claim on d5. Instead of mirroring White with 2...Nc6, Black prepares ...d5, so an early f4 can be met by a counterblow in the center rather than by grabbing the pawn. The idea echoes the Falkbeer Countergambit of the King's Gambit. The engine considers the position roughly balanced and prefers 3. Bc4, 3. Nf3 and 3. g3.

The most combative try is 3. f4, widely called the Vienna Gambit online, although that name traditionally belongs to 2...Nc6 3. f4 exf4. Here capturing with 3...exf4 is dubious, because 4. e5 forces the knight back to g8; even 4...Qe7 runs into 5. Qe2 with the same retreat. Black instead plays 3...d5, and after 4. fxe5 Nxe4 a sharp position arises: White has a cramping pawn on e5, Black a centralized knight. Common fifth moves are 5. Nf3, the traditional main line, 5. Qf3, associated with Spielmann, and 5. d3, once neglected but now frequent; 5. Qe2 is Paulsen's move. The chief deviation is 4. exd5, when 4...exf4 can transpose into King's Gambit Accepted lines and 4...e4 reaches the old main line of the Falkbeer Countergambit, while 4. d3 is the Steinitz Variation. Anthony Santasiere and Weaver Adams promoted the gambit, but Raymond Keene judged it too risky for grandmaster play. In online games, White nonetheless scores better with 3. f4 than with the other main moves.

The most frequent reply is 3. Nf3, which steers into the Three Knights line of Petrov's Defense, or into the Four Knights Game after 3...Nc6. The Stanley Variation, 3. Bc4, keeps f4 in reserve and adds pressure on d5. Taking on e4 with 3...Nxe4 invites 4. Qh5, the Frankenstein-Dracula Variation, or 4. Nf3, the Boden-Kieseritzky Gambit, while 3...Nc6 4. d3 produces the quieter Berlin-Vienna Hybrid. Black can also choose 3...Bc5, the Spielmann Attack, or 3...Bb4, the Reversed Spanish.

Among the positional options, the Mieses Variation, 3. g3, typically continues 3...d5 4. exd5 Nxd5 5. Bg2 Nxc3 6. bxc3, leaving White with a fianchettoed bishop and an extra central pawn on the c-file. The Mengarini Variation, 3. a3, rules out ...Bb4, though Black's bishop can simply go to c4. 3. d3 aims for a King's Indian Attack setup, and the rare 3. f3, the King's Head Opening, scores poorly for White.