Nimzo-Indian Defense: Rubinstein System

The Nimzo-Indian Defense: Rubinstein System is a chess opening classified under ECO code E40 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 4 moves: 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3. The resulting position leaves black to move.