ECO D37 · Queen's Gambit Declined
Queen's Gambit Declined: Three Knights Variation
The position after 1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3.
1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Nc3
Queen's Gambit Declined: Three Knights Variation is filed under ECO D37, a variation of Queen's Gambit Declined. It is the position after 1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 — 7 half-moves in, with Black to move. From here theory names 5 continuations: Nbd7, c6, dxc4, Bb4, c5.