Chess Openings Lab
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Nimzo-Indian Defense: Kmoch Variation

The Kmoch Variation of the Nimzo-Indian is 4.f3, a pawn move that prepares e4 before Black can stop it. White wants a big center with e4 and is ready to accept doubled c-pawns, while Black hits the center at once with ...c5 or ...d5.

Moves
1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.f3
ECO
E20
Engine
−0.10 · level (Stockfish 17.1, depth 20)
Played
458 games in our lichess sample
White scores
54.3%

Key ideas for both sides

White

  • Push e4 next if Black allows it, so the f3 pawn supports a broad center on d4 and e4.
  • Answer ...c5 with a3, asking the b4 bishop to choose between a trade on c3 and the retreat ...Ba5.
  • After a bishop trade on c3, recapture bxc3 and use the bishop pair plus the half-open b-file.
  • In the main engine line, Qd4 centralizes the queen after the trades and eyes the g7 pawn.

Black

  • Strike with 4...c5 right away, so that e4 can be met by pressure on d4 and c4.
  • Use ...d5 to stop e4 for good; after cxd5 exd5 the f3 pawn looks out of place.
  • Trade with ...Bxc3+ when White plays a3, then target the doubled c-pawns with ...Na6, or ...b6 with the bishop heading to a6.
  • Castle short early. The f3 pawn has weakened the e3 square and the g1-a7 diagonal for White.

Plans and pawn structure

The f3 pawn decides the plans. White wants e4, and with pawns on d4, e4 and f3 the center gets very large, but the king's knight loses f3 and development is slow. Black should open lines before White finishes: ...c5 and ...d5 fight for e4 and d4. If White gets bxc3, the c4 pawn becomes a target for ...Na6, ...b6 and the c8 bishop on a6. If Black waits, White builds with e4, Bd3 and Ne2 and gets a free hand.

Where the engine's main line heads: White has doubled c-pawns. White's c-pawns are doubled, usually after ...Bxc3 bxc3. In return White keeps the bishop pair and a solid center.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position −0.10: level. Its three top choices for Black:

  1. −0.10 4...c5 5.a3 Ba5 6.dxc5 Bxc3+ 7.bxc3
  2. +0.09 4...d5 5.a3 Bxc3+ 6.bxc3 O-O 7.cxd5
  3. +0.11 4...O-O 5.a3 Bxc3+ 6.bxc3 d5 7.cxd5

Pawns, from White's side.

How it scores on lichess

458 rated lichess games reached this position; White scored 54.3%.

1600–199954.8%
2000 and up52.1%

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

Where it goes next

  • Sämisch Variation, Romanovsky Variation4...d5 · rare

How to play against it

Black, hit the center before e4 comes. The engine likes 4...c5, and 4...d5 is a solid choice that rules out e4. Do not play slowly with a queenside fianchetto while White pushes e4. When White plays a3, decide between ...Ba5 and ...Bxc3+ based on whether c4 can be attacked.

Questions

What are the moves of the Nimzo-Indian Defense: Kmoch Variation?

The Nimzo-Indian Defense: Kmoch Variation starts 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.f3. Its ECO code is E20.

Is the Nimzo-Indian Defense: Kmoch Variation good for White?

Stockfish 17.1 rates the position −0.10 at depth 20, which is level. In 458 lichess games from our sample, White scored 54.3%. A rare but direct choice for White players who want a big center, and Black should meet it with quick central counterplay.

What is the main idea of the Nimzo-Indian Defense: Kmoch Variation?

White plays f3 to force through e4 and build a big center, accepting slower development. Black answers with ...c5 or ...d5 and often trades on c3 to aim at the doubled c-pawns.

What should Black play next?

The engine's first choice is c5, with d5 and O-O close behind. 4...c5 attacks d4 at once, before White has time for e4, a3 and a calm setup.

Updated October 2026. Sources and method.