The document discusses the emergence and development of the Byzantine Empire and Orthodox Christianity following the fall of the Western Roman Empire. It notes that the Byzantine Empire, with its capital at Constantinople, survived invasions and disease that destroyed Rome. The Byzantine Empire influenced Eastern Europe through trade, its military, and by spreading Orthodox Christianity. It eventually declined due to invasions and lost Constantinople to the Ottoman Turks in 1453, but had spread Orthodox Christianity and its cultural influences to places like Kievan Rus, the predecessor state to Russia.