Roman diocese

A Roman or civil diocese (Latin: dioecēsis, from the Greek: διοίκησις, "administration") was one of the administrative divisions of the later Roman Empire, starting with the Tetrarchy. It formed the intermediate level of government, grouping several provinces and being in turn subordinated to a praetorian prefecture.

The earliest use of "diocese" as an administrative unit was in the Greek-speaking East. Three districts, Cibyra, Apamea, and Synnada, were added to the Province of Cilicia in the time of Cicero, who mentioned the fact in his epistles. The word "diocese", which at that time denoted a district pertinent for the collection of taxes, was applied to the territory per se.

The reorganization of the Roman Empire known as the Tetrarchy was initiated by Emperor Diocletian in the AD 290s. He divided the Provinces into smaller, more compact, and easily governed units, with a greatly increased bureaucracy. The Provinces were in turn grouped into 12 dioceses, each headed by a vicarius ("dioceseos"), i. e. a deputy to the Praefectus praetorio ("Praetorian Prefect"). The Dioceses themselves were grouped into 4 huge prefectures, each one headed by a powerful Praefectus praetorio. Under the Tetrarchy, each of the 2 senior Emperors, the Augusti, governed a praetorian prefecture. The largest diocese by number of provinces, not area, was the Diocese of the East, which included 16 provinces, while the smallest, the Diocese of Britain, comprised only 4 provinces.

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