ECO D37 · Queen's Gambit Declined
Queen's Gambit Declined: Three Knights, Vienna Variation
The position after 1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 dxc4.
1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Nc3 dxc4
Queen's Gambit Declined: Three Knights, Vienna 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 dxc4 — 8 half-moves in, with White to move. From here theory names 3 continuations: e4, Bg5, e3.