English Defense: Hartlaub Gambit Declined

The English Defense: Hartlaub Gambit Declined is a chess opening classified under ECO code A40 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 5 moves: 1. c4 e6 2. d4 b6 3. Nc3 Bb7 4. e4 f5 5. d5. The resulting position leaves black to move.