warrio warriors. they came as simply people who want to help people, educate people religiously. >> reporter: isis nishlly appealed to syria's deeply conservative rebel units who entrusted protecting the town to them. we were all on the front lines fighting, he tells us, and then we realized that with the situation in the town under isis, they were exerting their control through terrorism and punishment. a tactic isis repeated in an effort to en trench itself. this man is a syrian who wants his face and voice concealed. he defected from isis. their main stronghold in the east. they think he's dead. the syrian who were with isis thought they were the purist organization around, he says. their jihadi principles matched ours.