How did the Sunni-Shia split begin?

The divide goes back to a question of succession after the Prophet Muhammad died in 632: who should lead the community he left behind. Those who accepted the choice of Abu Bakr as first caliph came to be called Sunnis. Those who held that Ali, Muhammad's cousin and son-in-law, should lead came to be called Shias. A political disagreement later hardened into a religious one. [1] [2] [3]

By his death in 632 Muhammad had consolidated power in Arabia, and the BBC describes a community of about one hundred thousand Muslims organised as a state. According to the Council on Foreign Relations, some argued that leadership should go to a qualified individual, while others insisted the legitimate ruler must come through Muhammad's bloodline. A group of prominent early followers chose Abu Bakr, a companion of Muhammad, as the first caliph, over the objections of those who favored Ali. [1] [2]

The names came from these camps, though the BBC notes they were used only later. Shia comes from shi'atu Ali, meaning partisans of Ali. Sunni refers to followers of the sunna, the way of Muhammad. Both groups agree that Muhammad was the final prophet, so the caliphs and imams were successors, not prophets. [2] [1]

The BBC says both Sunnis and Shias have good evidence for their understanding of the succession. Sunnis point out that Muhammad asked Abu Bakr to lead congregational prayers while he lay on his deathbed, which they take as a sign he was naming Abu Bakr. They also hold that caliphs were chosen through political processes rather than named explicitly by the Prophet, according to Project MUSE. [2] [4]

Shias cite reports that on the way back from his last Hajj Muhammad took Ali's hand and told his Companions that anyone who followed him should follow Ali. They understand this as appointing Ali as his sole interpreter, in political and spiritual terms. Shias came to believe in a chain of imams descended from Muhammad through Ali, which is the imamate, as opposed to the Sunni caliphate. The sources describe these as the two communities' own accounts and do not say which is correct. [2] [4]

According to the BBC, Ali did not at first pledge allegiance to Abu Bakr but did so months later, in both Sunni and Shia belief, to keep the new state united. Umar and Uthman followed as caliphs. Ali became the fourth caliph in 656 after Uthman was murdered, and the period brought the Battle of the Camel and the indecisive Battle of Siffin against Mu'awiya, the governor of Damascus. Ali was assassinated in 661 by a Kharijite, one of a group that had broken from his camp over his acceptance of arbitration. [2] [3]

Mu'awiya then took the caliphate to Damascus and founded the Umayyad dynasty. In 680 Ali's son Husayn, the third Shia Imam, was killed with his companions at Karbala by forces of the Umayyad caliph Yazid. The CFR says Karbala became a defining moral story for Shias, and that Sunni rulers' fear of the Imams led to further persecution and marginalization of Shias. Wikipedia's summary of the topic likewise says a political split became a more personal one. [2] [1] [5]