Iraqi army and militia forces are fighting to take back Tikrit from the so-called Islamic State. Pulling the strings on the Iraqi side is an Iranian: Major-General Qassem Suleimani, the 'shadow commander' who has been described as the single most powerful operative in the Middle East. As the leader of the foreign branch of Iran's Revolutionary Guards - the Quds Force - Suleimani has emerged as Iran's leading foreign strategist. He has been arming and training Bashar al-Assad's military in Syria and leading the Shia militias fighting ISIS on the frontline in Iraq - where the US blames him for countless attacks on American soldiers. He has the ear of the supreme leader and has been influencing politics from Yemen to Bahrain. Mark Coles tells his extraordinary story.

Producer: Chloe Hadjimatheou