ECO E21 · Nimzo-Indian Defense
Nimzo-Indian Defense: Three Knights Variation
The position after 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Nf3.
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Nf3
Nimzo-Indian Defense: Three Knights Variation is filed under ECO E21, a variation of Nimzo-Indian Defense. It is the position after 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Nf3 — 7 half-moves in, with Black to move. Named theory ends here; beyond this the position is yours to work out.