Queen's Gambit Declined: Modern Variation, Knight Defense
ECO D51
Move order
1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. Bg5 Nbd7
Ideas
ECO D covers queen-pawn games and closed structures, including many Gambits and the Queen's Gambit complex. White builds a pawn center and keeps the position more closed than after 1. e4. This entry tracks a longer branch in the opening tree. Use the diagram and SAN list to recognize the tabiya, then try the line against Maia to explore typical plans in practice.