The Expansion of Islam from Mecca, Medina and the Hijaz region began with the Prophet Muhammad's death in 632. This had been prefigured by his letter to Emperor Heraclius inviting him to accept submission to God--Islam. At Muhammad's death tribes newly joined to his polity tried to break away, and the subsequent punitive expeditions--Ridda Wars--phased into the dramatic conquests of all of the Sassanian and much of the Byzantine lands. By 635, Damascus and Homs were in Muslim Arab hands, and after the resounding defeat of Byzantine forces at the Battle of the Yarmuk (636), Palestine and the rest of Syria were open to Islam. Jerusalem and Antioch were taken in 638, at which point Islamic armies began both westward and eastward offensives. By the 650s, Egypt was taken, as was North Africa to Cyrenica, where Berbers resisted fiercely at first, later converting to Islam, allowing the subjugation of Tunisia and Carthage by 695. In the East, after the momentous Battle of Qadisiyya on the Euphrates in 637, Ctesiphon fell, as did Mosul in 641. A further Sassanian defeat at Nahavand in 642 opened up the entire Iranian plateau. Qazvin and Ray near Tehran were taken in 643. Persepolis was conquered in 650, and Arab Muslim armies had reached Merv on the Oxus River by 651. In the next thirty years, Arab Muslim raids would course throughout Byzantine Anatolia, ravaging regions in Cappadocia, as well as Nicaea in western Asia Minor on a regular basis. In 687 Arab armies laid siege to Constantinople for the first time, in aspired-to fulfillment of Prophetic dicta.
Spain had been under Visigoth control since the middle of the fifth century. At first, they were not well received by the local population, being Arian as opposed to the majority's Catholicism. Within a century, they had accepted Catholicism and received in return clerical cooperation. Still, political technology was limited, and weak or young-perishing kings had not been able to weld together a coherent state. Also, persecution of the growing Jewish population removed their potential support. Thus, after Arab armies had consolidated their hold on North Africa and begun converting the interior's Berbers to Islam, the Arab-Turkish Muslim Amir (commander) Tariq, crossed over to Gibraltar (Jabal-Tariq, the mountain of Tariq), and launched a nine-year conquest of Iberia up to the Pyrenees (711-20), annihilating the Visigothic state. Provence and Aquitane were now raided frequently. During the same years, on Islam's northeastern borders, adventurous Amirs conquered Transoxiana, beyond the Oxus River, and the Oxus delta by 715, while in the south, Sind, in present-day Pakistan, was taken by 713. Back in the European sphere, only Charles Martel's defeat of Muslim forces in the Battle of Tours near Poitiers in 732, combined with Leo III's defeat of Muslim besiegers at Constantinople in 717, halted the new religious polity's advances, until ninth century forays into the Mediterranean.
In addition to these advances in the foreign realm were changes in the Islamic polity's--Dar al-Islam--internal make-up. Upon Muhammad's death, immediately a crisis emerged related to who should rule the new political-religious unit. He had gathered around him in fifteen or so years of preaching close colleagues. Many of them were acquired in Mecca. One of the closest was Ali, a cousin. As well, there were supporters who had come to the banner later, in Medina. While Muhammad was being prepared for burial by Ali, Meccan companions--the muhajirun, those who had migrated with the Prophet to Medina--were entangled in succession debate with Medians--ansar, or those who assisted the muhajirun on their arrival in Medina. In order to prevent further strife, Umar, a prominent member of Muhammad's own tribe and an early convert, convinced his colleague and kinsman Abu Bakr to become leader of the Muslims. His title was khalifa (Eng. Caliph), or successor to Muhammad, the Messenger of God. Whereas the majority of ansar and muhajirun accepted his candidacy, an undercurrent of opposition continued, claiming that Ali was entitled, being close to Muhammad, pious, and perhaps even nominated by the Prophet as his successor. Umar (r. 634-44) succeeded him, and presided over the first wave of conquests. This brought large numbers of non-Muslims under their control. Those Christians and Jews among them were dubbed people of the book and were allowed to practices their religions freely, though were made to pay a special tax called the jizya. To this protected category were later added Zoroastrians, a sign of Islamic pragmatism. As well, great numbers of non-Arabs converted to Islam, and were called mawali, or clients of the original Arab conquerors.
Along with continuing sentiment in favor of Ali, dissension began to permeate the Islamic state during the tenure of Caiph Uthman (644-656). He was a member of the leading branch of the Quraysh tribe in Mecca, the branch that had actively opposed Muhammad's mission prior to 632. He reasserted the tribal aristocratic prerogatives, appointing family-members to nearly every possible position, among them Muawiya as governor of Syria. When Uthman was assassinated by soldiers from Egypt, some members of the Ummayad branch suspected the new Caliph Ali as the chief conspirator. Muawiya became the standard-bearer of this group, openly rebelling against the Iraq-based Ali by 658 as an anti-Caliph. They eventually met in battle, and though Ali's forces were prevailing, he agreed to arbitration. The arbitrators were disposed towards Muawiya, so the proceedings did not go well for Ali. By 661, on Ali's death, Muawiya was able to establish himself as Caliph, founding the hereditary Ummayad dynasty of Caliphs centered in Damascus. It was he and his descendents that directed the next phase of conquest and laid siege to Constantinople. However, from this time forwards, permanent political rifts developed in the Islamic world, now called umma or super-tribe. A group called 'Partisans of Ali' evolve into the Shi'ite form of Islam (Shia: Party or Faction). They believed that only Ali had had legitimate rights of succession to Muhammad. Further, only Ali's descendants were entitled to be Caliph. This premise, as well as early Ummayad massacre of Ali's son and successor Husayn and his supporters at Karbala in 686, caused them to view all Islamic political leaders except Muhammad and Ali as illegitimate. The exception were the Imams, or direct descendants of Ali, the twelfth of which went into occultation, or temporary disappearance, in 987.
The Ummayad dynasty lasted until 751. It was the particularly Arab period of Islam. Arabs were accorded precedence in all matters, with new non-Arab uslims, or mawali, being forced into subservient roles. In some cases, taxes akin to jizya were imposed on them. As for non-Muslims, Ummayads did not encourage their conversion, recognizing their financial benefit.
During the 740s, dissension in the Islamic east among non-Arabs mounted, especially in Persia, which possessed a rich civilizational history and resented upstart Arab domination. Certain dissidents in the East, such as Abu Muslim, were able to galvanize generalized support for Ali as well, under the auspices of a new faction from the Quraysh called the Abbasids. By the end of the decade, enfeebled Ummayad Caliphs were not able to put down growing rebellion in Iraq and Persia, such that the Abbasids were able to come to power in 751, claiming to be the upholders of true Islamic piety blind to ethnicity, as well as the cause of Ali, which they jettisoned in the next decades.