Identify this empire with capital in modern day Istanbul.
Its enemies ranged from the Bulgarian king Samuil and the Persian Sassanids to the Umayyad caliphs and Attila the Hun. Byron called its culture "the Triple Fusion": the body of a Roman, the mind of Greek, and the soul of a mystic. In the early years, its leaders included (*) Zeno, a barbarian ruler who held his territory together even as the Ostrogoth Odoacer sacked the capital of his compatriots to the west. Later rulers Heraclius, Basil II and Justinian expanded the territory of the empire, only to see their gains melt away when their successors took the throne. Identify this empire with capital in modern day Istanbul.
Its enemies ranged from the Bulgarian king Samuil and the Persian Sassanids to the Umayyad caliphs and Attila the Hun.
Byzantine Empire or Eastern Roman Empire (accept Constantinople before *)