Falkbeer Countergambit, Modern Transfer

Instead of the traditional 3...e4 pawn sacrifice of the Staunton Line, Black simply captures on f4 with 3...exf4. Material is level, since each side has taken a pawn. Each side is left with doubled pawns: White on the d-file, Black on the f-file. The e-file is open, and Black's pawn on f4 still cramps White's kingside. The name reflects its main job: after 4. Nf3, by far the most common reply, the game transfers into the Modern (Abbazia) Defense of the King's Gambit Accepted, normally reached by 2...exf4 3. Nf3 d5 4. exd5.

From there Black seeks quick piece play rather than clinging to the f4-pawn, typically with 4...Nf6 attacking d5. White often answers with the check 5. Bb5+, and 5...c6 6. dxc6 bxc6 7. Bc4 Nd5 is the Botvinnik Variation. Theory credits White with a slight edge thanks to the extra central pawn, but the engine rates the position as roughly balanced, and decisive results split almost evenly. The rarer 4. Nc3 and 4. c4 avoid the transposition, but Black has scored well against both. The engine's other preferences are 4. Bb5+ and 4. Qf3.