Réti Opening: Anglo-Slav Variation, London Defensive System

The Réti Opening: Anglo-Slav Variation, London Defensive System is a chess opening classified under ECO code A12 in the Flank Openings family, characterized by moves like 1.c4, 1.Nf3, or 1.f4, aiming to control the center indirectly. It is reached after 4 moves: 1. c4 Nf6 2. g3 c6 3. Nf3 d5 4. b3 Bf5. The resulting position leaves white to move.