This system often leads to typical isolated queen's pawn (IQP) positions, with White gaining rapid development, a grip on e5, and kingside attacking chances to make up for the long-term structural weakness of the isolated d4 pawn. The major variation in this line 4...Nf6 5.Nc3 e6 6.Nf3, when Black's main alternatives are 6...Bb4 (a position which often transposes into lines of the Nimzo-Indian defence) and 6...Be7, once the most common line. 6...Nc6?! is inferior as it is favourably met by 7.c5!, after which White plans on seizing the e5-square through the advance of his b-pawn to b5 or by exchanging the Black's Knight on c6 after Bb5.