Roman Province - Diocletian's Reforms

Diocletian's Reforms

Emperor Diocletian introduced a radical reform known as the Tetrarchy (284–305), with a western and an eastern Augustus or senior emperor, each seconded by a junior emperor (and designated successor) styled Caesar, and each of these four defending and administering a quarter of the Empire. In the 290s, Diocletian divided the Empire anew into almost a hundred provinces, including Italy. Their governors were hierarchically ranked, from the proconsuls of Africa proconsularis and Asia through those governed by consulares and correctores to the praesides. These last were the only ones recruited from the equestrian class. The provinces in turn were grouped into (originally twelve) dioceses, headed usually by a vicarius, who oversaw their affairs. Only the proconsuls and the urban prefect of Rome (and later Constantinople) were exempt from this, and were directly subordinated to the tetrarchs.

Although the Caesars were soon eliminated from the picture, the four administrative resorts were restored in 318 by Emperor Constantine I, in the form of praetorian prefectures, whose holders generally rotated frequently, as in the usual magistracies but without a colleague. Constantine also created a second capital, Nova Roma, known after him as Constantinople, which became the permanent seat of the Eastern government. In Italy itself, Rome ceased to be the imperial residence, Mediolanum (modern Milan) and later Ravenna being favoured by the emperors. During the 4th century, the administrative structure was modified several times. Provinces and dioceses were split to form new ones, the praetorian prefecture of Illyricum was abolished and reformed, and changed hands between East and West several times. In the end, with the death of Theodosius I in 395, the permanent division of the Empire into Western and Eastern halves was complete.

Detailed information on these arrangements is contained in the Notitia Dignitatum (Record of Offices), a document dating from the early 5th century. Most data is drawn from this authentic imperial source, as the names of the areas governed and titles of the governors are given there. There are however debates about the source of some data recorded in the Notitia, and it seems clear that some of its own sources are earlier than others.

It is interesting to compare this with the list of military territories under the duces, in charge of border garrisons on so-called limites, and the higher ranking Comites rei militaris, with more mobile forces, and the later, even higher magistri militum.

In the longer surviving Eastern Empire, which is today conventionally labeled the Byzantine Empire to avoid scholarly confusion, this administrative subdivision was gradually changed. Justinian I made the first great changes in 534–536 by abolishing, in some provinces, the strict separation of civil and military authority that Diocletian had established. This process was continued on a larger scale with the creation of extraordinary Exarchates in the 580s and culminated with the adoption of the military theme system in the 640s, which replaced the older administrative arrangements entirely.