“Muqtada al Sadr, the radical Shia cleric who battled US forces during the Iraqi occupation, is preparing his militia to participate in an offensive to retake the northern city of Mosul from the Islamic State. The US military is preparing to aid the Iraqi government in liberating Mosul, but has insisted that the operation will not include the Shia militias.”
Source: Sadr’s ‘Peace Brigades’ prepares for Mosul offensive | The Long War Journal