Chess Openings Lab
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Nimzo-Indian Defense: Three Knights Variation

The Three Knights Variation of the Nimzo-Indian is 4.Nf3, a developing move that keeps every option for White. White can switch to Bg5, e3 or Qa4 plans, while Black castles and chooses between ...b6, ...c5 and ...d5.

Moves
1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Nf3
ECO
E21
Engine
+0.10 · level (Stockfish 17.1, depth 20)
Played
1,446 games in our lichess sample
White scores
52.6%

Key ideas for both sides

White

  • Play Bg5 after ...O-O, as in the top engine line, to pin the f6 knight and develop fast.
  • Answer ...d5 with Qa4+, gaining time and forcing ...Nc6 before White plays e3.
  • Set up with e3, Bd3 and O-O if Black plays ...b6, and aim for e4 later.
  • After ...cxd4 exd4, use the open lines and the active pieces; the isolated pawn on d4 supports Ne5.

Black

  • Castle with 4...O-O and wait for White to commit to Bg5, e3 or Qa4+.
  • Play ...c5 and ...cxd4 to give White an isolated d-pawn, then blockade it with ...d5.
  • Choose ...b6 and ...Bb7 for a calm game with control of e4.
  • Against Qa4+, block with ...Nc6 and use the queen's early move to develop quickly.

Plans and pawn structure

With Nf3, White keeps several systems ready and Black must choose too. If White plays Bg5 and e3, Black often answers with ...c5 and ...cxd4, leading to an isolated d4 pawn after exd4. Then White plays for active pieces and Ne5, while Black blockades d5. If Black goes ...b6, White builds with Bd3 and O-O and plays for e4. The Qa4+ idea after ...d5 is a way to gain time and keep the center flexible.

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...O-O 5.Bg5 c5 6.e3 cxd4 7.exd4
  2. +0.11 4...b6 5.e3 O-O 6.Bd3 d5 7.O-O
  3. +0.13 4...d5 5.Qa4+ Nc6 6.e3 O-O 7.Qc2

Pawns, from White's side.

How it scores on lichess

1,446 rated lichess games reached this position; White scored 52.6%.

under 120067.7%
1200–159951.4%
1600–199953.9%
2000 and up49.4%

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

Where it goes next

  • Romanishin Variation, English Hybrid4...c5 · rare

How to play against it

Black, castle and stay flexible with 4...O-O; it fits every setup White picks. If White plays Bg5, ...c5 and ...h6 are good answers. Avoid early ...d5 without a plan for Qa4+. In the isolated pawn structure, aim pieces at d4 and trade minor pieces.

Questions

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

The Nimzo-Indian Defense: Three Knights Variation starts 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Nf3. Its ECO code is E21.

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

Stockfish 17.1 rates the position +0.10 at depth 20, which is level. In 1,446 lichess games from our sample, White scored 52.6%. A flexible line for White players who like to choose a system move by move, and Black must know several setups.

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

White develops the king's knight and keeps several setups ready, including Bg5, e3 and Qa4+. Black castles and chooses a structure based on White's next move.

What should Black play next?

The engine's first choice is O-O, with b6 and d5 close behind. 4...O-O keeps every option and waits for White to commit with Bg5 or e3.

Updated October 2026. Sources and method.