BYZANTIUM, THE EASTERN Roman Empire, is unique in world history as the only territorial empire to have lost three-quarters of its lands and maintained its political identity for another seven centuries. The immense importance of the history of the seventh through ninth centuries cannot be lost on us, as it was during this time when the last of the three great global monotheisms of today emerged in the Arabian Peninsula and, after defeating the major political powers of western Eurasia, came to dominate most of the Mediterranean world. The first followers of Islam, a “community of believers” in the words of Fred Donner, challenged the two superpowers of the day in western Eurasia— the Persian Sasanian and Byzantine empires. In a series of decisive encounters, these challengers would defeat both empires and drive Byzantium from its lands in the Levant, Egypt, and Africa.

When one looks at the map of Byzantium of the Early Middle Ages (see Map 10), what is immediately arresting is the loss of territory the empire suffered after the sixth century, when it had controlled lands from the southern tip of Spain, North Africa, and Italy to Egypt and the Levantine sea coast. Equally noteworthy is the loss of control over the interior of the Balkan Peninsula, which the empire had essentially abandoned in the seventh century. Indeed, it has been recently suggested that most former imperial territories north of the Haemus (Balkan) mountains, were depopulated. East Roman political and economic power was based on the sea and dependent on control of it, notably naval dominance of shipping. Five seas— the Black, Marmara, Aegean, Adriatic, and Mediterranean— provided the sinews by which Byzantine political and economic influence was maintained. Indeed, the material evidence especially indicates that the maritime possessions of the empire, namely coastal Asia Minor, Italy, Sicily, Crete, and the Crimea, passed through the tumultuous years of the seventh and eighth centuries if not unscathed, then more populous and perhaps even materially more advantaged than has been previously thought.

The traditional narrative of Byzantium in the seventh and the first half of the eighth centuries as a moribund state, eclipsed by the neighbouring Muslim caliphate which dominated western Eurasia, is a compelling one. Throughout the seventh century, the Byzantines had lost an estimated three-quarters of their people and state revenues.