Nimzowitsch Variation

The Nimzowitsch Variation is Black's most frequent answer to 4. Bd2 in the Bogo-Indian. Rather than exchanging on d2 or retreating, 4...Qe7 defends the attacked bishop and leaves White to decide whether to resolve the tension. The queen on e7 suits a setup with ...d6 and ...e5, contesting the dark squares after the bishops leave the board. White's most popular reply is 5. g3, preparing a kingside fianchetto. 5. a3 questions the bishop at once, and 5. Nc3 is the third main choice.

After 5. g3 Nc6, two lines stand out. In 6. Nc3 Bxc3 7. Bxc3 Ne4, Black gives up the bishop pair and uses the knight to challenge the c3-bishop. In 6. Bg2 Bxd2+ 7. Nbxd2 d6 8. O-O a5 9. e4 e5, the pawns lock in the center and play turns on maneuvering. Both lines are considered equal. The engine gives White a small edge, and online results are close to even.