In the year 632 CE, the Prophet Muhammad died.  By this time Islam had spread, from Medina and Mecca westward to parts of the Arabian peninsula.  After Muhammad's death, his closest companion, Abu Bakir was elected, and ruled as caliph until 634 CE.  Upon Abu Bakir's death, the second elected Caliph, Umar, began his rule of the nascent Islamic Empire, overseeing its expansion between the years 634-644 CE.  Umar, determined to unite Arab tribes and foreigners alike under a peaceful ummah, or community, extolled his forces to fight only for bounty and not for conversion, and prohibited his armies from seizing newly acquired Arab lands, stationing them outside of and away from conquered communities.  

Umar's beneficence, and the emphasis on community values that the growing religion promoted, made Islam a popular monotheistic faith in the region, where Arab, Jewish, and Christian people had traditionally lived together, quadrupling the size of the Empire.  As a result, by the time of his death in 644 CE, the Empire spanned modern-day Syria, Egypt, and Tunisia and stretched as far as the Iberian Peninsula and the Sind, where the southern Indus valley was threatened by his troops. Devout soldiers spreading Muhammad's message of peace and surrender to Allah energized converts to fight alongside them, while conquered people were allowed to retain their property, various faiths, and local customs.  "The objective of Umar and his warriors was entirely pragmatic: they wanted plunder and a common activity that would preserve the unity of the ummah."

Uthman ibn Affan was the fourth elected caliph of the Islamic Empire.  And although he did not posses Umar's military prowess, the empire continued to expand, solidifying its positions on the Iberian peninsula, conquering Cyprus, and rousting the Byzantines from the Eastern Mediterranean. But by the time of Uthman's death six years into his caliphate, two factions within the Muslim world had emerged.  One of these, the Shi'ite, were less egalitarian than their more politically minded compatriots, the Sunni, who advocated for the relatively peaceful expansion of Islamic governance.  The moderate Sunni's prevailed, instituting a hereditary dynasty called the Umayyad, and installing the first appointed caliph.  This split, known as the first fitnah, resounds today, and marked the end of the rule of what are known as The Rightly Guided Caliph's.

Bibliography

Armstrong, Karen. Islam: A Short History. New York, New York. Modern Library. 2002.

Fritz.  "Islam After Muhammad's Death."