After Mohammad’s death in 632, the conquerors and their conquered were ruled by an earthly leader called caliph or ‘successor to the messenger of God’. And here is where the trouble begins.
Because Mohammad had no sons and because the Quran contained no clear instructions on how a successor should be chosen, the question of the leadership of the community was open to differing interpretations.
The early converts to Islam who had suffered with Mohammad in Mecca and participated in the hejira to Medina preempted all other claimants by naming one of their own, Abu Bakr, as the new head of the community. He was simply called the successor or khalif (anglicized as caliph.)
Eventually the term caliph came to designate the religious and political leader of the Islamic community, and the office became known as the caliphate. Abu Bakr (632-634) and two of his successors, Umar (634-644) and Uthman (644-656), are known in Islamic history as the Rashidun or ‘rightly guided’ caliphs in recognition of their personal closeness to the Prophet and their presumed adherence to Quranic regulations.
Nevertheless, although the caliphs were charged to provide both spiritual and temporal leadership, they were not the religious heirs of Mohammad who was known as the Seal (or last) of the Prophets. It soon became clear that they had no inherent spiritual qualifications.
Gradually, they lost their religious aura.
Movements emerged to restore ‘the true doctrine of Islam’ as well as to overthrow the existing political order. One such movement was Shi’ism, one of the two main branches of Islam in the world today. The other branch is the Sunni mainstream branch.
Shi’ism had its roots in a succession struggle which occurred in 656 AD. At this time, a group of mutinous soldiers killed the third caliph, Uthman, and the succession issue re-emerged. It was resolved only after a civil war left an enduring schism within the Islamic ummah or community.
Ali, Mohammad’s cousin and the husband of the Prophet’s daughter Fatima, became caliph. He represented a broad coalition of interests calling for greater equality among all Muslims — both Arab and non-Arab — and for the restoration of the leadership of the community to the house of Mohammad. Nevertheless, his right to the caliphate was contested. Even though in some quarters of the ummah, the belief existed that Mohammad had intended for Ali to be his immediate successor, the community was divided.