Main Line

With 3...Qe7 Black brings a second attacker to bear on the e5-pawn, which only the f3-knight defends. This forces White to choose between returning the pawn for development and holding it with 4. Qd5, the Stockholm Variation, which exposes the queen. The drawback of Black's scheme is that the queen on e7 hems in the f8-bishop and can become a target. Kārlis Bētiņš introduced the line and Henri Grob employed it regularly. Engines give White a clear advantage, but on Lichess the results are exactly level.

The most popular reply is 4. Bf4, which seems to protect the pawn but runs into 4...Qb4+, hitting both the bishop and b2. After 5. Bd2 Qxb2 the correct 6. Nc3 develops with gain of time, while 6. Bc3?? walks into 6...Bb4!, for example 7. Qd2 Bxc3 8. Qxc3 Qc1#. Following 6. Nc3, the knight sortie 6...Nb4? fails to 7. Nd4 c6 8. a4, so the main line is 6...Bb4 7. Rb1 Qa3. Here 8. Nd5, which Grob had judged unclear, was shown by Stefan Bücker in 2006 and later by Boris Avrukh to give White a large advantage. Black can also answer 4. Bf4 with 4...d6 5. exd6 Qf6. In practice Black scores better than White after 4. Bf4, as many games end in the traps before the refinements arise.

The second most common choice, 4. Nc3, gives the pawn back at once. After 4...Nxe5 5. e4 White has a lead in development and the black queen is poorly placed; Bücker recommends 5...Nf6 6. Bg5 c6 7. Nxe5 Qxe5 8. f4 Qe6, a playable position that still favors White. Another option is 5. Bf4 Nxf3+ 6. gxf3 d6 7. e4, again with the better game for White. Viktor Korchnoi won a quick game in a 1978 simultaneous display with 5. Nd5 Nxf3+ 6. gxf3 Qd8 7. Qd4 d6 8. Bg5, though Bücker considers 8...f6 9. Bd2 c6 10. Nf4 Qb6 adequate for Black. White scores better after 4. Nc3 than after 4. Bf4. The third option, 4. Bg5, develops while attacking the queen.

The Stockholm Variation, 4. Qd5, is the only way to keep the extra pawn. The position after it was the mandatory starting point of the thematic tournament sponsored by Fritz Englund in 1932–33. Black usually strikes at the pawn with 4...f6, since 4...b6 and 4...h6 do not give enough compensation.