Unlike the split between Catholics and Protestants that caused mayhem in Europe when the Reformation demolished fifteen centuries of Catholic monopoly, the divide in Islam between Sunnis and Shias was present from the very beginning. As Toby Matthiesen explains in this clearly written, nuanced and meticulously documented book, the dispute over the succession to the Prophet Muhammad following his death in 632 has been present throughout Islamic history and remains unresolved to this day. 

While the argument between Sunnis and Shias has some theological dimensions, with Shias (like Catholics) adopting a more hierarchical system of religious authority than their Sunni counterparts, the original dispute was primarily over a fundamental question of governance. Should the leadership of the infant Islamic community have devolved to Muhammad’s cousin and son-in-law Ali, husband of his daughter Fatima, and his descendants? Or should it have passed to his close companion Abu Bakr, father of his young widow, Aisha (and in some accounts, a bitter rival to Fatima), in his capacity as caliph, or successor, to the Prophet? Supporters of Ali became known as Shias, while supporters of Abu Bakr and the caliphs after him acquired the name Sunnis. Shias had their own disputed successions, with those known as Seveners or Ismailis favouring Ismail as the seventh imam (hereditary leader) in descent from Ali, while the larger group, known now as Twelvers, accept Ismail’s brother Musa instead.

The critical event leading to the split between Sunnis and Shias was the killing of Ali’s son Husayn by Umayyad forces at the Battle of Karbala in 680, an event Shias still commemorate with public flagellations and passion plays. Most of the Shia imams, with a single exception, were murdered