Nimzo-Indian Defense · E43

St. Petersburg Variation, after 4. Nf3, through 9. O-O

1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 b6 5. e3 Ne4 6. Qc2 Bb7 7. Bd3 Bxc3+ 8. bxc3 f5 9. O-O

The structure hands White the half-open b-file - rook pressure down it is a standing plan. Black's queenside bishop takes the long diagonal. ...Bb4 pins the knight that supports e4: Black fights for the light squares, often trades on c3 to damage the pawns, and plays structure against the bishop pair.

The first 4 moves, explained

• 1. d4 Stakes a claim in the centre, controlling e5, and frees the bishop and queen.
• 1... Nf6 Develops the knight to f6, eyeing d5 and e4.
• 2. c4 Fights for d5 from the flank - contesting the centre without committing a centre pawn.
• 2... e6 Supports the centre, adding control of d5.

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