Which region did the byzantine empire control for the longest period?

The Empire of Nicaea is considered the legitimate continuation of the Byzantine Empire because they managed to re-take Constantinople. Theodosius was the last emperor to rule over both the Eastern and Western Roman Empire.

it took two men to wrestle rome back from chaos and turn a republic into an empire. in the first century bc, rome was a republic. power lay in the hands of the senate, elected by roman citizens. but the senators were fighting for power between themselves.