Nimzo-Indian Defense, Classical Variation

The Nimzo-Indian begins when Black's bishop goes to b4 and pins the knight on c3: the knight cannot move without opening the diagonal toward White's king. In the Classical Variation, White's queen moves to c2, written Qc2 in algebraic notation. The main idea is to play a3 and, if the bishop captures the knight, recapture on c3 with the queen instead of the b-pawn.

That recapture preserves an orderly pawn structure and gives White the bishop pair, meaning both bishops remain while Black has exchanged one for a knight. The queen also helps control e4, a useful square for building a larger center.

The concession is time. The queen develops early, may have to move again, and does not help White's kingside pieces. Black often secures the king and challenges the center with the d- or c-pawn. Unlike the Rubinstein System, which begins with e3 and frees the king's bishop, this line prioritizes structure and control of e4.