The Byzantine period starts with the division of the Roman empire to East and West. The division of the empire into East and West and the subsequent collapse of the Western Roman Empire were developments that constantly accentuated the position of the Greeks in the empire and eventually allowed them to become identified with it altogether. The leading role of Constantinople began when Constantine the Great turned Byzantium into the new capital of the Roman Empire, from then on to be known as Constantinople, placing the city at the center of Hellenism a beacon for the Greeks that lasted to the modern era.
The Byzantine Empire was the predominantly Greek-speaking eastern half continuation and remainder of the Roman Empire during Late Antiquity and the Middle Ages. Its capital city was Constantinople, originally founded as Byzantium (hence the term Byzantine). It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until it fell to the Ottoman Turks in 1453. During most of its existence, the empire was the most powerful economic, cultural, and military force in Europe.
Several events from the 4th to 6th centuries mark the transitional period during which the Roman Empire's east and west divided. Under the reign of Heraclius (610-641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin. Thus, although it continued the Roman state and maintained Roman state traditions, modern historians distinguish Byzantium from ancient Rome insofar as it was oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity rather than Roman polytheism.
Although the Byzantine Empire had a multi-ethnic character during most of its history and preserved Romano-Hellenistic traditions, it became identified by its western and northern contemporaries with its increasingly predominant Greek element. The occasional use of the term "Empire of the Greeks" (Latin: Imperium Graecorum) in the West to refer to the Eastern Roman Empire and of the Byzantine Emperor as Imperator Graecorum (Emperor of the Greeks) were also used to separate it from the prestige of the Roman Empire within the new kingdoms of the West.