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Chess Opening Theory/1. d4/1...d5/2. c4/2...dxc4/3. Nf3/3...Nf6/4. e3/4...e6/5. Bxc4
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Queen's Gambit Accepted D25-D29
5. Bxc4
White recaptures the pawn while developing the light-squared bishop. This also allows White to quickly castle kingside.
Black should try to stay active and strike at the center with /5...c5/.
Black could also play /5...a6/, trying to get in 6...b5 with a tempo on White's bishop. The move a6 is also part of the main line and therefore likely to transpose with 6. O-O c5.
Theory table
5. ... c5 6. O-O a6 5. ... a6 6. O-O b5
References
See also
Queen's Gambit Accepted 3...Nf6_4.e3