411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e6/2. d4/2...d5/3. Nc3/3...Bb4/4. e5/4...c5/5. a3/5...Bxc3
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Winawer variation C17-C19 Winawer variation
5...Bxc3+
Black takes the pinned knight to avoid having his bishop boxed in. White's only plausible reply is /6. bxc3/.
References
French Defence