In order to systematize the administration of the vast Empire, which included many races, Diocletian introduced the system of tetrarchy, of the power of four persons. The administrative power was divided between two Augusti, who had equal plenipotence. One of them was to live in the eastern, and the other in the western, part of the Empire; but both had to work in the interests of one Roman state. The Empire remained undivided; the appointment of two Augusti, however, indicated that the government recognized even in those days that a difference existed between the Greek East and the Latin West, and that the administration of both could not be entrusted to the same person. Each Augustus was to be assisted by a Caesar, who, in case of the death or retirement of the Augustus, became the Augustus and selected a new Caesar. This created a sort of artificial dynastic system which was supposed to do away with the conflicts and conspiracies originating in the ambitions of various competitors. This system was also meant to deprive the legions of their decisive influence at the time of the election of a new emperor.
The first two Augusti were Diocletian and Maximian, and their Caesars were Galerius and Constantius Chlorus, the father of Constantine the Great. Diocletian retained his Asiatic provinces and Egypt, with headquarters at Nicomedia; Maximian kept Italy, Africa, and Spain, with headquarters at Mediolanum (Milan); Galerius kept the Balkan peninsula and the adjoining Danubian provinces, with a center at Sirmium on the River Save (near present Mitrovitz); and Constantius Chlorus kept Gaul and Britain, with centers at Augusta Trevirorum (Trier, Treves) and Eburacum (York). All four rulers were considered as rulers of a single empire, and all government decrees were issued in the name of all four. Although theoretically the two Augusti were equal in their power, Diocletian, as an emperor, had a decided advantage. The Caesars were subjects of the Augusti. After a certain period of time the Augusti had to lay down their titles and transfer them to the Caesars. In fact Diocletian and Maximian did lay down their titles in 305 and retired to private life. Galerius and Constantius Chlorus became the Augusti. But the troubles which followed put an end to the artificial system of tetrarchy, which had already ceased to exist at the beginning of the fourth century.
A History of the Byzantine Empire - Table of Contents
Next Chapter : From Constantine to the Early Sixth Century
Previous Chapter : The foundation of Constantinople
Reference address : https://www.ellopos.net/elpenor/vasilief/reforms-diocletian-constantine.asp?pg=3