Early Origins of the Shi'a /Sunni Divide

Islam, not unlike Christianity, isnot a homogeneous religion but split into two large 

branches Sunni and Shi'i Islam, each with their own offshoots.

While the history of the divide goes back nearly to the rise of Islam, the effects of this division are still seen to this day. 

Source: Council on Foreign Relations

Origins of the Divide

In the year 632 the prophet Muhammed died. Muhammed was more than a religious figure: through his establishment of the Muslim community or ummah, he became an important political leader in the area as well. His death left the ummah without a leader-- a position which needed to be filled. As Muhammed was the "seal of the prophets," the leader would not be a prophet himself. But how to choose? Some followers of Islam said that Muhammed had designated 'Ali-- his son-in-law, cousin, and devoted follower to be his successor. Many others insisted he had not named a successor  and companions of the prophet gathered together to appoint a  new leader.

During the meeting ('Ali was not present), 'Umar a charismatic leader from the ummah, went up to Abu Bakr and gave him his support as leader or khalifa [successor]. According to the shiite tradition, 'Ali gave Abu Bakr his support after he was elected in oder to preserve the unity of the ummah. 

'Umar Source: Wikipedia 

Abu Bakr served as caliph from 632-634, and 'Umar is chosen as his successor during the period of 634-644. After 'Umar is killed by a Persian slave in 644 there are two strong candidates for khalifa: 'Uthman and Ali. Ultimately, 'Uthman is selected to succeed 'Umar and serves from 644-656 when he is killed during riots by his own people. 

'Uthman Source: Wikipedia

'Ali succeeded 'Uthamn in 656 during a troubled time in the caliphate. Some of the ummah felt that Ali had not performed his duties in avenging the death of 'Utham. Talha and ibn al Zubayr found Ayesha, one of the prophet's widows, and together they plotted against 'Ali. This resulted in the Battle of the Camel near Basr in present day Iraq. Talha and ibn al Zubayr are killed and Ayesha returned to medina. This divided the ummah.

'Ali: Source: Wikipedia

'Ali realized the consequences of this division and sought the support of Mu'awiya, the governor of Syria, who was well respected.  Mu'awiya did not feel that 'Ali had properly avenged the death of 'Uthman and refused his support. The two met in battle in 657, known as the Battle of Siffin. Mu'awiya's forces were loosing and at the suggestion of one of his military commanders, 'Amr ibn Al-As, had his men place pages of the Qu'aran on their lances and hold them up, which confused the opposition and stopped the fighting. 'Ali and Mu'awiya decided to enter into negotiations and each send a man to deliberate as to wether or not Ali had fully avenged the death of 'Uthman.

Negotiations determined 'Ali had not fully avenged the death of 'Uthman. Some of the followers of 'Ali, known after as the kharijites, left his camp after this incident because they felt he was at fault for allowing things to go into negotiation. 'Ali starts to massacre some of the kharijites which causing more trouble in the ummah. He also decides to go after Mu'awiya which many find dishonorable as the negotiations were legally binding. In 661, Ali is stabbed to death in a mosque near Kufa.

                                         The Imamate

Source: University of North Carolina Chapel Hill

Shi'ias believe in a form of government of the caliphate known as the Imamate, starting with 'Ali. The Imams are religious and political leaders who are often given some deity like qualities such as the ability to perform miracles.  Arguments over who was the true Imam  have caused further branching of Shiism. 

Source: Wikipedia

The Caliph

Sunnis believed in the caliph as a political leader, and the ulema or religious scholars as the spiritual leaders of the ummah. 

Conclussions

This is a very basic overview of the early origins of the Shi'a/ Sunni divide. There are many more events that take place in Islamic history that deepen these divides but this is a blog post and not a history book.  It is also important to note that while there is a schism not all Shi'as and Sunnis live in rivalries. In some places they do co-exist peacefully, and even intermarry. 

Historical dates and information taken from Professor Pulcini's Islam lecture, Fall 2014 at Dickinson College.