Among the thousands of militia fighters who flocked to northern Iraq to battle the extremist Islamic State group over the summer was Qais al-Khazali.

Like the fighters, al-Khazali wore green camouflage. But he also sported a shoulder-strapped pistol and sunglasses and was flanked by armed bodyguards. When he was not on the battlefield, the 40-year-old Iraqi donned the robes and white turban of a cleric.

Al-Khazali is the head of a militia called Asaib Ahl al-Haq that is backed by Iran. Thanks to his position he is one of the most feared and respected militia leaders in Iraq, and one of Iran's most important representatives in the country.