Subdivisions of the Byzantine Empire

The subdivisions of the Byzantine Empire were administrative units of the Eastern Roman or Byzantine Empire (330–1453). The Empire had a developed administrative system, which can be divided into three major periods: the late Roman/early Byzantine, which was a continuation and evolution of the system begun by the emperors Diocletian and Constantine the Great, which gradually evolved into the middle Byzantine, where the theme system predominated alongside a restructured central bureaucracy, and the late Byzantine, where the structure was more varied and decentralized and where feudal elements appeared.

Source: Wikipedia — Subdivisions of the Byzantine Empire (CC BY-SA 4.0)