Catalan Opening: Open Defense

The Catalan Opening: Open Defense is a chess opening classified under ECO code E04 in the Indian Defences family, where Black responds to 1.d4 with 1...Nf6, including the Nimzo-Indian, Queen's Indian, and King's Indian. It is reached after 5 moves: 1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. g3 c6 5. Bg2 dxc4. The resulting position leaves white to move.