White can develop his pieces in a number of ways in the Exchange Variation. For decades, theory held that the correct method of development was with Bc4 and Ne2, often followed by 0-0 and f4–f5, playing for a central breakthrough or kingside attack. It was generally thought that an early Nf3 was weak in the Exchange Variation because it allowed Black too much pressure on the centre with ...Bg4. In the late 1970s, however, Karpov, Kasparov and others found different methods to play the Exchange Variation with White, often involving an early Rb1 to remove the rook from the sensitive a1–h8 diagonal, as well as attempting to hinder the development of Black's queenside. Another, relatively recently developed system involves quickly playing Be3, Qd2, and Rc1 or Rd1 to fortify White's centre, remove White's rook from the diagonal, and possibly enable an early d5 push by White.