The Three Knights Variation, Korchnoi Variation is a variation of the Nimzo-Indian Defense, catalogued as ECO E21. The line runs 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 c5 5. d5, reaching the position shown below after 9 half-moves.
White holds the centre with pawns on d5, and one pawn capture is available, so the structure has not settled yet. Development is level at two minor pieces each. It is Black to move after five moves.
On the Nimzo-Indian Defense generally: One of the most respected defenses to 1.d4. Black pins the knight and fights for central control.
You can play through this variation move by move in your browser — Learn mode walks the line with an explanation at each step, and Drill mode replays it from memory so you find out whether you actually know it. No account is required.
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The Three Knights Variation, Korchnoi Variation goes 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 c5 5. d5. It is a variation of the Nimzo-Indian Defense and is catalogued as ECO E21.
The Three Knights Variation, Korchnoi Variation is ECO E21. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Nimzo-Indian Defense.
Stockfish evaluates the position after 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3 c5 5. d5 at -0.11 at depth 18, which is balanced. Engine evaluation is only a starting point — at club level the practical value of a line is mostly about whether you know its plans better than your opponent does.
White holds the centre with pawns on d5, and one pawn capture is available, so the structure has not settled yet. Development is level at two minor pieces each. It is Black to move.