While the Arabs of northern Arabia were uniting as a capable fighting force looking for opportunities to expand, the Byzantines and Sasanian Empires were at a low ebb. In the early seventh century, the Byzantine Empire had won a long and costly war against the Sasanians, sometimes fought on both sides by proxies from northern Arabia, but now the combatants were exhausted and financially drained. Meanwhile, Muhammad’s historic unification of the majority of Arab tribes under the single leader of a monotheistic faith was only the beginning of the story of Islam. After Muhammad and his followers were forced to flee Mecca for Medina in 622, fighting between the two communities continued for several years before those in Mecca converted to Islam, and Muhammad made a triumphant return to the city. The stage was now set for a significant shift in the balance of power in the region.
The issue of leadership following Muhammad’s death caused immediate tensions within the Islamic ummah even as the first four caliphs, the Rashidun, oversaw significant territorial expansion. Tensions between the family of Muhammad—especially his son-in-law Ali, the fourth caliph—and the Umayyads resulted in a civil war that brought Islam’s first dynasty to power.
Within a century of Muhammad’s death, an Islamic state ruled over the world’s largest empire at that time, first unifying the Arabian Peninsula through the Ridda Wars and then taking territory previously ruled by the flagging Byzantine and Sasanian Empires. Mimicking the leadership and culture of their Byzantine and Persian predecessors as a means to legitimize their own role, the Umayyads began the process of articulating what made Islamic culture unique among the other cultures of the region. By the later period of their rule, they began to privilege the position of the ethnically Arab members of the empire and to increasingly “Arabize” the government and its functions, despite the fact that the Arab-Muslim conquerors remained a minority population and did not promote or support the conversion of non-Muslims to the new faith.
Through a process of conquest, conversion, and coexistence, the early Abbasids created a cosmopolitan medieval empire centered at their new capital of Baghdad. By assimilating the late antique traditions of the Byzantines and Persians before supplanting them, integrating Arab culture northward throughout the region, and overseeing the preservation and dissemination of knowledge from the ancient world, the Muslims of the Middle East created a thriving cultural hub with considerable impact on world history in this period and beyond. While religious conversion to Islam remained slow, a process of cultural conversion and an increased openness to non-Arab converts to the faith saw the escalation of Islamization throughout the Abbasid empire from Spain and Portugal in the west to India in the east.