'ABU JAFAR AL-MANSUR was taking no chances with his new imperial capital, for this was to be a city like no other. The second Abbasid caliph of the Muslims turned for guidance to his trusted royal astrologers, the former Zoroastrian Nawbakht and Mashallah, a Jew turned Muslim from Basra and now ``the leading person for the science of judgments of the stars.'' The pair consulted the heavens and declared that July 30, 762, would certainly be the most auspicious day for work to begin. Still, al-Mansur hesitated. He ordered his architects to mark the layout of the walls of his proposed city – a perfect circle, in keeping with the geometric teachings of the caliph's beloved Euclid – on the ground, first in ashes and then again with cotton seeds soaked in naphtha. This was set ablaze to create a fiery outline of the so-called Round City, the geometric center of al-Mansur's future metropolis.
At last, the caliph was satisfied. ``By God! . . . I shall live in it my entire life, and it shall become the home of my descendants; and without a doubt, it will become the most prosperous city in the world,'' declared al-Mansur, Arabic for ``the victor- ious.'' Abbasid coins and other official usage celebrated al-Mansur's capital as the Madinat al-Salam, or ``the city of peace,'' but among the people it always retained the name of the old Persian settlement that had been on the same spot—Baghdad.
Twelve years before work began on the capital, al-Mansur's brother Saffah completed the overthrow of the Umayyad dynasty, which had risen to power in the Muslim world three decades after the death of the Prophet Muhammad in 632. In the revolutionary retribution that followed, Saffah - "shedder of blood" - sent his forces under the Abbasid's distinctive black banners to hunt down the remaining members of the House of the Umayyads. The only significant figure to escape alive was Prince Abd al-Rahman, who fled to North Africa before going on to establish the future Western Caliphate in southern Spain. But the victory of the rebels, who found it politically expedient to assert their direct lineage to the Prophet through his paternal uncle Abbas, was less a blood feud between an aging dynasty and an ambitious pretender than it was a wholesale cultural revolution throughout the Islamic lands.
Well before the Abbasid victory in 750, the armies of Islam had successfully retraced the path of Alexander the Great, one thousand years earlier, pushing across the Oxus River into Afghanistan and reaching India and western China. The conquest of Persia, to the east of the Umayyad capital, was complete by 651, and soon Muslim power was extending westward as well, through North Africa and into Spain. As a result of this rapid territorial expansion, Muslim Arabs no longer enjoyed a majority in the empire under their control. Now they had to contend with a daunting patchwork of ethnic and religious communities: large urban populations of Persians, both recent Muslim converts and traditional Zaroastrians; Aramaic speakers, Christians and Jews alike; Arab Christians of various stripes, including many "dualist" sects that had broken with Eastern Orthodox Byzantium; and other groups.
Many of the empire's newest Muslims, especially those in the traditionally Persian lands, were openly skeptical of the Umayyad claims of political and religious legitimacy. The early Umayyad caliphs were descended from members of teh Prophet Muhammad's inner circle but were not his blood relatives, something that did not always sit well with the Persian converts and other newcomers of the faith. They responded enthusiastically to rebel propaganda that asserted direct family links between the Abbasids and the Prophet and demanded "an acceptable ruler" from the family of Muhammad. With the final collapse of the old order at the hands of the Abbasids, the way was open to a range of newcomers - notably Persians, but also Sabeans, Jews, and many others - to assume an increasingly influential role in the intellectual and political affairs of the empire.
Territory seized from the Byzantines create an inviting haven for Syiran Jacobites, Nestorians, and other Christians, who in the seventh and eighth centuries began to flee Constantinople's enforced religious orthodoxy and increasing animosity toward ancient learning. Christian scholars were suddenly free to explore and develop classical teachings under the protection of the Muslims, who traditionally imposed a poll tax on those "People of the Book" - generally Jews and Christians but also Zoroastrians - who chose not to convert to Islam but otherwise left them alone. Important intellectual centers thrived across the region, from Edessa to the Iranian city of Jundishapur, from Harran, in present-day Turkey, to the Central Asian oasis town of Marv, offering Abbasids a formidable body of indigenous linguistic skills, scientific talent, and cultural knowledge.
Muslim conquest and empire building also restored ancient ties among historic centers of civilization across a huge landmass. This created an invaluable melting pot for intellectual traditions that had been forcibly kept apart for centuries by political divisions: Hellenistic learning that evolved in Greece and, later, Alexandria, on the one hand, and Sumerian, Persian, and Indian wisdom on the other. Muslims, Christians, Jews, Zoroastrians, the star-worshipping Sabaeans, and assorted other pagans were all able to exchange ideas and teachings. Under Abd al-Rahman, the surviving Umayyad prince, and his successors, this same intellectual tradition put down deep roots in Muslim Spain. There, its guardians would one day hand over priceless gifts to the army of Latin scholars who, fired by the example of Adelard of Bath, set off on their own hunt of the studia Araburm.'
--Jonathan Lyons, The House of Wisdom