Nimzo-Indian Defense, Kmoch Variation

The Kmoch Variation is defined by f3, meaning White's f-pawn advances one square. That pawn supports a future e-pawn move to e4, intending to place two pawns together in the center and gain space. It directly challenges Black's control of e4 by the knight on f6 and bishop on b4.

The plan is ambitious, but f3 does not develop a piece. It also occupies the king knight's natural square and weakens part of the king's future shelter. White must decide how to complete development and where to place the king before Black opens the center with the d- or c-pawn.

White often adds a3 to attack the bishop on b4. If Black captures on c3 and White recaptures with the b-pawn, the game may reach structures from the Sämisch Variation. Reaching the same position through another move order is called a transposition.