English Defense: Hartlaub Gambit Declined
ECO A40
Move order
1. c4 e6 2. d4 b6 3. Nc3 Bb7 4. e4 f5 5. d5
Ideas
ECO A covers irregular and flank openings—systems that skip the main e4/d4 fight early. White controls d5 without committing the d-pawn—the English family. 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.