Nimzo-Indian - 4.e3
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3 O-O 5. Nf3 d5 6. Bd3 b6
White advances the queen's pawn to d4. Black develops the knight to f6. White pushes the c-pawn to c4.
Black moves the king's pawn to e6. White develops the knight to c3. Black develops the dark-squared bishop to b4.
White pushes the king's pawn to e3. Black castles kingside. White moves the knight to f3.
Black moves the queen's pawn to d5. White develops the light-squared bishop to d3. Black pushes the b-pawn to b6.