The city of Constantinople, among the most distinctive and consequential European creations of late antiquity, presents itself as a witness to the various transformations that take place between the fourth and the ninth centuries CE. Late antiquity, especially as it relates to Europe, may accordingly be characterized as a period of disruption, transition, and transformation away from a Mediterranean-centered, late Roman imperial political and socioeconomic order. The expansion of the late Roman state apparatus and its increasing claim upon the economy has traditionally been seen as causes of economic crisis and decline. Attempts in the sixth century to regain lost Roman territories in the western Mediterranean achieved limited success. Like the Romans, the Umayyads relied upon local elites for the collection of taxes. In the Roman period, trade in amber led from the southern shores of the Baltic to central Europe and the Black Sea.

The Umayyad dynasty fell rapidly in the face of the Hashimite-Khurasani revolution in 132/750, the Abbasid dynasty's hold on power took until 145/762 to become firmly established. Baghdad was meant to be the fortress of the new dynasty in times of crisis, as well as a strategically situated city in times of peace in economic and political terms. Iraq was the wealthiest province of the empire, and had been undergoing a process of agricultural development since the Umayyad period. Al-Mahdi's decade-long reign was by all accounts a prosperous time for the caliphate. When the Abbasid succession passed on to Harun al-Rashid, it was finally the anticipated moment which different factions wanted. After achieving reconciliation with the Abbasid family and granting amnesty to former opponents in Baghdad, al-Mamun dispatched Abd Allah ibn Tahir on the mission of reunification. Just as al-Mamun's political achievements radically transformed the Abbasid government, his religious policies were equally new and daring.