BAGHDAD (AP) — Iranian-backed Shiite militias and Sunni tribes have joined Iraq's military in a major operation to retake Saddam Hussein's hometown from the Islamic State group, while the U.S.-led coalition has remained on the sidelines. The campaign for Tikrit is a dress rehearsal for the real contest: The fight to recapture Mosul, Iraq's second-largest city and the extremists' biggest stronghold.