Nimzo-Indian - Saemisch variation
1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. a3 Bxc3+ 5. bxc3
White pushes the queen's pawn to d4. Black develops the knight to f6. White moves 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 a-pawn to a3. Black captures with the dark-squared bishop on c3, giving check. White captures on c3 with the b-pawn.