At the end of the Fourth Century, the Roman Empire was divided into 4 units (Prefectures) for the purposes of the civil government.
Source: History of the Later Roman Empire, by J.B. Bury.
I. Prefecture of the Gauls:
(Britain, Gaul, Spain, and northwestern corner of Africa)
Dioceses (Governors):
- A. Britain
- B. Gaul
- C. Viennensis (Southern Gaul)
- D. Spain
II. Prefecture of Italy:
(Africa, Italy, provinces between the Alps and the Danube, and the northwestern portion of the Illyrian peninsula)
Dioceses (Governors):
- A. Africa
- B. The Italies
- Vicarius urbis Romae
- Vicarius Italiae
- C. Illyricum
III. Prefecture of Illyricum:
(Dacia, Macedonia, Greece)
Dioceses (Governors)
- A. Dacia
- B. Macedonia
IV. Prefecture of the East or Oriens:
(from Thrace in the north to Egypt in the south and the territory of Asia)
Dioceses (Governors):
- A. Thrace
- B. Asiana
- C. Pontus
- D. Oriens
- E. Egypt
