The Byzantine Empire

The date 476 CE gets treated as an ending, and in certain textbooks it still does. A Germanic chieftain named Odoacer deposed the last emperor of the western provinces, a teenager named Romulus Augustulus, and sent the imperial insignia to Constantinople rather than bother appointing a successor. Western Rome was over.

But the eastern half had not fallen. It kept going. Its armies kept campaigning. Its laws kept functioning. Its bureaucrats kept taxing. Its emperor kept issuing coins stamped with his face. In Constantinople — the city Constantine had refounded on the old Greek town of Byzantion in 330 CE — the Roman state simply continued, without interruption, for another nine hundred and seventy-seven years.

That is the central fact of Byzantine history, and it tends to disorient people who learned that Rome fell. Rome fell in the west. In the east, it persisted, adapted, and over centuries became something genuinely distinct from the empire Augustus had ruled — different language, different theology, different court culture, different enemies — while insisting, with complete sincerity, that it was still Rome. The word "Byzantine" was invented by later historians. The people who lived in this empire called themselves Romans until the day it ended.