Byzantium, or the City of Constantine - Constantinople, the "New Rome" of the Eastern Empire, was destined to become the capital of the Byzantine or Medieval Greek Empire from the early fourth century AD. It was intended to play a dominant role in the historical development of the peoples and nations of the southeastern Mediterranean basin for approximately eleven and a half centuries until, shortly after the mid-fifteenth century, another great power, the Ottoman Turks, coming from the East, replaced the Byzantine Empire in this critical period. Throughout its long duration, the Byzantine Empire managed to survive through countless external threats from the West, the North, and the East amidst many internal disturbances. In parallel, it managed to create a great self-sufficient culture and civilization, with remarkable achievements in literature, sciences, and arts. The main characteristics of this unique civilization were not only the ancient Greek and Hellenistic heritage and the Greek Orthodox Christian tradition but also the transformative social, institutional, economic, and cultural changes and reforms that gradually transformed the late Roman state into a clearly medieval Greek state. The beginning of the Byzantine Empire inaugurates the history of medieval Hellenism, while its final fall coincides with the dawn of modern Hellenism through the difficult centuries of Ottoman rule.