The Battle for Tikrit

The Iraqi military -- backed by at least 20,000 Shiite militiamen -- is fighting to regain control of Saddam Hussein's hometown of Tikrit, one of several predominantly Sunni towns to fall to the militants last year. It's one of the first major operations in which the U.S.-led coalition is not taking part, with U.S. officials saying they weren't ask to participate. Iranian advisers have played a prominent role on the front lines of Iraq's Salahuddin province.