Map – Eastern Roman (Byzantine) Empire
Even after the fall of the Western portion of the Roman Empire, the Byzantines still referred to themselves as Romans. Under Theodosius I, who reigned from 379–395, Christianity became the Empire’s official state religion and the older religions such as Roman polytheism were banned. Under Heraclius, who reigned from 610-641 AD, Greek replaced Latin as the official language.
The Byzantine Empire existed from 330 – 1204, when it was dealt a serious blow during the 4th Crusade. when Constantinople was sacked. The Empire then collapsed and split up into competing Byzantine Greek and Latin realms.The Byzantines had regrouped by 1261, and the Empire continued, in a much smaller version than before, until 1453, when Constantinople fell to the Ottomans.