Declined Variation

The Declined Variation is the most common answer to the Nimzowitsch Defense. Instead of occupying the center at once with 2. d4, White develops the king's knight and postpones d2-d4. This avoids the independent lines that Nimzowitsch players prepare, such as 2. d4 d5 3. e5 Bf5, and puts the choice to Black: enter mainstream theory or keep the game irregular. The engine rates the position as roughly balanced and prefers 2...e5, 2...d6 and 2...d5, in that order. White scores slightly better overall.

Nearly half of all games continue 2...e5, which reaches the position normally arising from 1. e4 e5 2. Nf3 Nc6, the King's Knight Opening: Normal Variation. White can then choose among the Ruy Lopez, the Italian, the Scotch and the other open games. For a Nimzowitsch player this means playing those main lines on White's terms. Other transpositions to established defenses tend to be less satisfactory, because the knight on c6 obstructs Black's usual pawn play.

The Franco-Nimzowitsch Variation, 2...e6, aims for a French structure in which the c6 knight rules out the standard ...c5 lever against White's center. The early 2...d5 produces a Scandinavian-type game, but the knight stands in front of the c-pawn, so ...c6 is not available to support Black's pieces. In online play this line nonetheless scores well for Black. The rare 2...g6 leads to an irregular form of the Modern Defense.

Black has two ways to stay in independent territory. The Williams Variation, 2...d6, is the more reliable. It resembles a Pirc in which Black's knight has already committed to c6, and after 3. d4 Black usually pins with 3...Bg4 to pressure d4. The sharper 4. d5 Ne5 5. Nxe5 is the Keene Attack. The Colorado Countergambit, 2...f5, challenges e4 immediately at the cost of loosening Black's kingside. Theory regards it as dubious, although it scores respectably in online games.