iranian-backed regime and looked at isis and some of them made the disastrous calculation that isis was the lesser of two evils. >> the last american soldier left the country in 2011. after the u.s. account not reach agreement with maliki to maintain a military presence. >> the question we asked when people look back is what would we have done with 10,000 years of troops. would they enforce security and would we have wanted them to be fighting in places like mosul? >> republicans have criticized president obama for not leaving troops in iraq. some said if american forces had stayed there would be no isis. emma sky believes that was never in the cards. iraq's prime minister maliki had a new set of patrons. his fellow shiites in tehran.