Two Knights Defense, Knight Attack

The Knight Attack, 4. Ng5, is White's most direct answer to the Two Knights Defense. With the f6-knight blocking the queen's path to g5, White's knight can land there unopposed and combine with the c4-bishop against f7 while Black's king is still uncastled. The move breaks the rule against moving one piece twice in the opening, and theory holds that Black neutralizes it with precise play; the engine rates the position as balanced. Players sometimes refer to the whole position loosely as the Fried Liver, or Fegatello, although that name belongs more properly to the knight sacrifice on f7 after 4...d5 5. exd5 Nxd5 6. Nxf7.

The threat is real: 4...h6 loses to 5. Nxf7 Qe7 6. Nxh8. The standard reply, chosen in roughly three quarters of games, is 4...d5, which shuts the bishop's diagonal at the cost of a pawn after 5. exd5. The main line then continues 5...Na5, the Polerio Defense, chasing the bishop: after 6. Bb5+ c6 7. dxc6 bxc6 8. Bd3 Nd5 9. Nf3 Bd6 10. O-O White keeps the extra pawn, but Black's pieces are freer and the position is judged to be level. The sharper 5...b5 (Ulvestad Variation) and 5...Nd4 (Fritz Variation) are less common, while 5...Nxd5, popular among amateurs, allows both the Fried Liver and the Lolli Attack, 6. d4.

Black's other main options meet the attack with a counterattack. 4...Bc5, the Traxler Counterattack, leaves f7 to its fate and targets f2; after 5. Nxf7 Bxf2+ 6. Kxf2 Nxe4+ Black has ample play, so the stronger reply is 5. Bxf7+, which collects a pawn and leaves the Traxler objectively suspect. 4...Nxe4, the Ponziani-Steinitz Gambit, is considered refuted by 5. Bxf7+ Ke7 6. d4, yet in online games Black scores better with it than with either 4...d5 or 4...Bc5, presumably because the refutation is hard to find at fast time controls.

The move appears in the analyzes attributed to Polerio and Greco, whose games already featured the knight sacrifice on f7. Masters generally prefer the quieter 4. d3, but 4. Ng5 remains one of the most frequently reached positions in online play and still surfaces at elite level, as in Zhongyi Tan's use of it at the 2026 Women's Candidates. In the Lichess database White wins slightly more than half the games and draws are rare.