Twelver Shiism – A branch of Islam that serves both as a spiritual and political force in Iran and beyond Twelver Shiism is the largest branch within Shiism - one of the two major sects within Islam. Shiism is the second-largest tradition within Islam overall, following the Sunni tradition. Iran is the only country to have Twelver Shiism as its official religion. In this tradition, religious leaders known as the maraji' al-taqlid - the highest-ranking cleric within Twelver Shiism - and other high-ranking clerics, including ayatollahs, are regarded as moral and...