Queen's Pawn Game: Colle System, Traditional Colle

The Queen's Pawn Game: Colle System, Traditional Colle is a chess opening classified under ECO code D05 in the Closed & Semi-Closed Games family, arising from 1.d4 d5, including the Queen's Gambit, Slav Defense, and related systems. It is reached after 5 moves: 1. d4 Nf6 2. Nf3 e6 3. e3 c5 4. Bd3 d5 5. c3. The resulting position leaves black to move.