Complex sentence: Levy also noted that prisoners could maintain many of their social customs and behaviors at Camp Douglas, which was impossible at Andersonville, and the garrison enforced discipline at Camp Douglas which deterred crime but the garrison at Andersonville rarely did so.
Split into simpler sentences: Levy also noted that prisoners could maintain many of their social customs and behaviors at Camp Douglas, which was impossible at Andersonville. The garrison enforced discipline at Camp Douglas, which deterred crime, but the garrison at Andersonville rarely did so.