Byzantine emperor Theodosius III abdicated in favour of Leo the Isaurian after he captured Theodosius's son. Byzantine Empire: The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Eastern part of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived the fall of the Western Roman Empire in the 5th century AD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'. March 25, 717. Wiki link