warmly treated by iraqi troops around tikrit, as a full-blown offensive appears imminent tikrit is the scene of the islamic state's bloodiest massacre executing 1700 iraqi soldiers on camera last june. success there is vital. >> it's all part of a campaign plan to go toward mosul. by the way, when you take a look at the concept of what isis is trying to do part of their desire for a caliphate is to gain ground and maintain it and govern it. so the gradual chipping away of that ground within iraq by a secure shia government is critically important. >> reporter: iran iraq and the united states simply make for strange bedfellows. the u.s. sees tehran as the most active state sponsor of terror. but in this battle they're