The most natural response to 3...Bb4+ is 4.Bd2. Black has a surprisingly large choice of moves: 4...Qe7 is the most popular, but 4...a5, 4...Bxd2+, and 4...c5 are also played. The less natural 4.Nbd2 prepares a grab for the Bishop pair, as in 4...b6 5.a3 Bxd2+ 6.Bxd2 or 6.Qxd2. The move 4.Nc3 transposes to the Nimzo Indian after 4...d5, or the Queen's Indian after 4...b6.


