Four Pawns Attack, Main Line

The Main Line arises when White meets 6...Nc6 with 7. Be3, defending d4 with a piece instead of 7. Nf3, which would allow the awkward pin ...Bg4. Black nearly always answers 7...Bf5, the bishop's only natural square, developing it before ...e6 closes its diagonal; 7...g6 and 7...e6 are rare. After 7...Bf5 8. Nc3 e6 9. Nf3, the knight protects e5 and supports a possible d5 advance. The main reply is 9...Be7, preparing ...f6. White used to answer with 10. d5 and complex play, but 10. Be2 O-O 11. O-O f6 12. exf6 Bxf6 13. Qd2 Qe7 14. Rad1 Rad8 15. Kh1 prevents ...e5, removes the king from the a7-g1 diagonal and leaves Black an isolated e6-pawn; White won Robson–Naroditsky, US Championship 2021, with it.

Other ninth moves are 9...Qd7, the Tartakower Variation, aiming at queenside castling and kingside play; 9...Bb4, active but less popular; and 9...Bg4, which spends a tempo to hit d4, though ...Bxf3 gxf3 gives White two bishops and more central support. Engines give White a slight edge, yet Black scores marginally better online.