411 REFERENCE · Wikibooks
Chess Opening Theory/1. d4/1...Nf6/2. c4/2...e6/3. Nc3/3...Bb4/4. a3/4...Bxc3
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Sämisch Variation E24-E29 Sämisch Variation
4...Bxc3+
Black takes the knight with 4...Bxc3+. White must recapture with /5. bxc3/. White will have the bishop-pair and a large center, but Black will have counterplay against the weak c4-pawn.
Theory table
5. bxc3 c5 6. e3 Nc6 5. ... ... 6. f3 Nc6 5. ... b6 6. f3 Nc6 5. ... O-O 6. f3 d5 5. ... d6 6. f3 c5 5. ... Nc6 6. f3 b6
References
See also
Nimzo-Indian Defence