Transpositions After 2...Bb4+
White can respond 3.Nc3, 3.Nd2 or 3.Bd2. The game often transposes to a Dutch Defence, a Nimzo-Indian Defence, a Bogo-Indian Defence, a Queen's Indian Defence, an English Defence, or a Queen's Gambit Declined. 3.Nc3 is likely to transpose into one of those openings: 3...Nf6 (Nimzo-Indian Defence), 3...f5 (Dutch Defence), 3...d5 (an unusual form of Queen's Gambit Declined), or 3...b6 (English Defence). Black has the same options after 3.Nd2, except that 3...Nf6 4.Nf3 is a Bogo-Indian Defense.
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