The later Roman Empire was a time of profound cultural, political, and religious transformations. Various crises in the Roman government, as well as the rise of Christianity, propelled these changes. In the third century CE, the emperor Valerian’s capture by the Sasanians was an indication of how easily the Roman Empire’s prominence could fluctuate and fissure (Figure 10.1). Stretching from the island of Britannia (Britain) in the Roman West to Syria in the Roman East, the empire continually struggled in its relationships with foreign groups on its eastern and western frontiers. The threatening presence of the Sasanians and other marginal states in the Mediterranean, including various Germanic kingdoms in the west and Palmyra in the east, reflected a new state of affairs.
The empire shifted its focus eastward, a trend signaled most prominently by its reorientation around its new capital in Constantinople (today’s Istanbul). The Romans then saw their power and sphere of influence shift as well. With a growing Christian population and shrinking borders, the entity that now became the Byzantine Empire persisted in the eastern Mediterranean. Yet it had to grapple with the migration of different groups through its territory as well as the disintegration of the western empire into small independent states. In addition, smaller states such as Aksum in sub-Saharan Africa and the Kushan Empire in central Asia came onto the scene during this period, establishing their own thriving societies away from the Mediterranean while being interconnected as neighbors and trade partners. The interrelationships among this multitude of states reflect the complicated circumstances of the Late Antique world.