Chess Opening Theory/1. e4/1...e6/2. d4/2...d5/3. Nd2/3...Be7

This is the Morozevich Variation in the French Defense. This is a sideline which has the idea to force Ngf3, not a comfortable place for the king's knight as he would rather be tucked at e2 to protect the d pawn. Hence, 4.Bd3 is the main line to delay the king's knight to establish itself on f3 and force and Nf6 and e5, to possibly transpose to the mainline.