Budapest Gambit Accepted, Main Line, Rubinstein Variation

With 4. Bf4 White defends e5 with a piece and prepares to answer ...Bc5 with e3 without shutting in the queen's bishop, which is the drawback of the Adler Variation, 4. Nf3. The bishop on f4 also helps cover the kingside, so the attacks Black often gets against the Adler arise less frequently. The line takes its name from Rubinstein–Vidmar, Berlin 1918, the first game with 4. Bf4. The cost is that the bishop is developed early. It is exposed to ...Bb4+ and can become a target for ...g5 and ...h5.

The main line is 4...Nc6 5. Nf3 Bb4+, intending ...Qe7. With 6. Nc3 White keeps the extra pawn, the bishop pair and central activity, but accepts a damaged queenside. With 6. Nbd2 Qe7 White returns the pawn for a sound structure. After 7. a3 White forces the exchange on d2, which yields the bishops, more space and a queenside minority attack. The alternative 7. e3 tries to gain a tempo, but the exchange on d2 may then come on worse terms or not at all. Black also has the gambit tries 6...f6 and 6...d6. The immediate 4...g5 attacks the bishop at once and scores better for Black on Lichess than the other replies. Engines give White a slight edge.