London System: Poisoned Pawn Variation

The London System: Poisoned Pawn Variation is a chess opening classified under ECO code D02 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 d5 3. Bf4 c5 4. e3 Qb6 5. Nc3. The resulting position leaves black to move.