English Opening: King's English Variation, Four Knights Variation, Korchnoi Line

The English Opening: King's English Variation, Four Knights Variation, Korchnoi Line is a chess opening classified under ECO code A28 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 e5 2. Nc3 Nf6 3. Nf3 Nc6 4. a3. The resulting position leaves black to move.