Advance Variation, Nimzowitsch System

The Nimzowitsch System is White's fourth-move alternative to the standard 4. c3 in the Advance Variation of the French Defense. Instead of preparing to meet ...cxd4 with a pawn recapture, White develops the king's knight, which covers d4 and also supports the pawn on e5. It is a different line from the Nimzowitsch Attack, 4. Qg4, although both are linked to Nimzowitsch's work on the Advance.

Without c3, White can no longer maintain a pawn on d4 once Black captures there. Recapturing with the knight is unattractive, because the knight then stops guarding e5 and the e-pawn becomes loose. For that reason White usually does not hurry to regain the pawn and continues developing instead. The typical sequences are 4...Nc6 5. Bd3 cxd4 6. O-O and 4...cxd4 5. Bd3 Nc6 6. O-O, which arrive at the same position. The knight stays on f3 to support e5, the bishop takes aim at the kingside, and White treats the d-pawn as an investment in time and development, much in the spirit of the Milner-Barry Gambit. Black's task is to decide how much to hold on to the extra pawn while completing development behind a still-cramped center.

Against 4. Nf3, Black most often plays 4...Nc6, chosen in more than half of the games. It increases the pressure on d4 and keeps the exchange on d4 in reserve; White can still add c3 and return to the structures of the Paulsen Attack. The immediate 4...cxd4, roughly a quarter of the games, settles the central question at once and asks White to show what the gambit approach offers. 4...Qb6 is a less frequent choice that attacks d4 and b2 at once. Engines also rate 4...Bd7, a developing move that keeps options open, among Black's best replies, along with 4...cxd4 and 4...Nc6.

The system is fairly common, especially in online play, where it ranks within the top two hundred named openings by number of games. Results favor Black, who scores about 52 percent against White's roughly 45, and the engine regards the position as approximately level. The play tends to be less theoretical than the main lines after 4. c3, but the open d-file and White's lead in development make it more dynamic.