Tetrarchy (286–305) Two major reforms to the administrative divisions of the empire were undertaken during the
Tetrarchy. The first of these was the multiplication of the number of
provinces, which had remained largely unchanged since the time of
Augustus, from 48 at the beginning of
Diocletian's reign to around a hundred by the time of his abdication. The multiplication of the provinces was probably undertaken for military, financial, and economic reasons. At the same time, the status of the provinces was regularized.
Egypt lost its unique status and was divided into three provinces, The provinces governed by
proconsuls (
Africa and
Asia) remained outside the vicars' jurisdiction,. as did the cities of Rome and Constantinople, which were governed by a
Praefectus urbi instead. The vicars had no military powers. Troops stationed in the dioceses fell under the command of a
comes rei militaris, who was directly under the control of the
magister militum and was in charge of the
duces who had the military command of individual provinces. Many modern scholars date the introduction of the dioceses to AD 296–297. A passage of
Lactantius, who was hostile to Diocletian because of his
persecution of the Christians, seems to indicate the existence of
vicarii praefectorum in the time of Diocletian: Thus Lactantius refers to the
vicarii praefectorum as being active already in Diocletian's time. Other sources from Diocletian's reign mention one Aurelius Agricolanus who was an
agens vices praefectorum praetorio active in
Hispania and condemned a centurion named Marcellus to be executed for his Christianity, as well as an Aemilianus Rusticianus, who is considered by some scholars to have been the first vicar of the Diocese of the East that we know of. Lactantius also mentions one Sossianus Hierocles as an
ex vicario active in the East in this period. Septimius Valentio is also attested as
agens vices praefectorum praetorio of Rome between 293 and 296. However, these sources do not prove that these
vicarii or
agentes vices were already in charge of dioceses with a well-defined and stable territory. The matter remains controversial.
Constantinian reforms (326–337) . From 310,
Constantine I was one of the
Augusti of the Empire and from 324 he was the sole ruler of the whole state. During his reign, he carried out many crucial reforms creating the administrative and military organization of the empire which would last until the
fall of the Western Roman Empire.
Regionalisation of the Praetorian Prefectures The principal territorial reform undertaken by Constantine, as part of a process of trial-and-error, was the 'regionalisation' of the
Praetorian prefecture. Hitherto, one or two
Praetorian prefects had served as chief minister for the whole empire, with military, judicial, and fiscal responsibilities. The political centralisation under Constantine, which culminated in the reunification of the whole empire under his rule, resulted in an "administrative decentralisation."
Paul Petit argues that the dioceses "themselves prefigured to some degree" the regional praetorian prefectures.
Creation of the The other reason for the weakening of the vicars was the regular dispatch of
comites, who outranked the vicars and probably had the role of inspecting their conduct. Under Emperor
Valens (364–378), the
Diocese of Egypt was split out of the Diocese of the East. In Italia,
Odoacer and then the
Ostrogothic kings, particularly
Theoderic, basically retained the Roman provincial system, including the Praetorian Prefecture of Italia and the two vicariates of Italia Annonaria and Italia Suburbicaria, as well as the various provinces that they contained. When Theoderic conquered
Provence in 508, he also re-established a Diocese of the Gauls, which was promoted to the rank of Prefecture with a capital at
Arelate two years later. This Praetorian Prefecture was abolished in 536, during the reign of
Vitiges, after the cession of Provence to the Franks. The rationale behind Odoacer and Theoderic's maintenance of the Roman provincial system was that they were officially viceroys of the Roman emperor in Constantinople, for whom Italia nominally continued to form part of the Roman empire. The civilian offices, including the vicars,
praesides, and Praetorian Prefects, continued to be filled with Roman citizens, while Barbarians without citizenship were barred from holding them. According to
Cassiodorus, however, the authority of the
vicarius urbis Romae was diminished: in the 4th century, he no longer controlled the ten provinces of Italia Suburbicaria, but only the land within forty miles of the City of Rome. For example, the
comes Orientis (count of the East) became the title of the governor of
Syria I, while the vicars of Asia and Pontus became governors of Phrygia Pacatiana and Galatia I respectively, with the title of
Comes Iustinianus and civilian and military powers. In May 535, Justinian abolished the vicariates of
Thrace and the Long Walls, in order to improve the defence of the Long Walls by ending the continuous conflicts between the two vicars. He entrusted the administration of the diocese of Thrace to a
praetor Iustinianus with civilian and military powers. Essentially, the modifications to the provincial system carried out by Justinian were motivated by the desire to end the conflict between civilian and military officials, and thus moved away from Diocletian's principle of completely separating civilian and military power. In this, according to
J. B. Bury, Justinian anticipated the introduction of the
themes in the 7th century. Moreover, by abolishing the dioceses, Justinian attempted to simplify the bureaucracy and simultaneously decrease the state's expenses, noting that the vicars had become superfluous, since their courts of appeal were used ever less frequently and the provincial governors could be directly controlled by the Praetorian Prefect, by means of the so-called
tractatores. Some of Justinian's decisions were subsequently revisited. In fact, thirteen years after the reforms of 535, in 548, Justinian decided to re-establish the diocese of Pontus due to serious internal problems. The vicar of Pontus was also given military powers, in order to effectively oppose the brigands that infested the region. In the same period, five provinces of the former diocese of Asia which had become infested with brigands (
Lycaonia,
Pisidia,
Lydia, and the two
Phrygiae), were placed under the jurisdiction of a
biocolytes (preventor of violence), in order to maintain order in the region. The jurisdiction of this official was reduced to just Lycaonia and Lydia in 553, since the other three provinces had been
pacified. The authority of the two Italian vicars was definitely much reduced compared to the 5th century.
Disappearance In the seventh century, as a result of the establishment of the first
themes (military districts governed by a
strategos with military and civilian authority) and the invasions of the Arabs and Slavs, the Praetorian Prefectures of the East and of Illyricum disappeared. The last certain attestation of a Praetorian Prefect of the East is in 629, while Illyricum survived to the end of the 7th century, but without any effective power since the majority of the Balkans, aside from
Thessaloniki, had fallen under the Slavs. Thus the Prefect of Illyricum was renamed the Praetorian Prefect of Thessaloniki. In the same period, the
dioceses of Dacia and
Macedonia finally disappeared as a result of the loss of almost all their territory. However, the
Taktikon Uspenskij which was written at the beginning of the 9th century, mentions a Praetorian Prefect of Constantinople and Proconsuls (
anthypatoi) of the themes, which suggests that the Praetorian Prefecture of the East continued to exist even though it had lost most of its earlier powers and had only a few judicial functions. If the dioceses lost their fiscal functions during the 6th and 7th centuries, it may be that they were replaced by new groupings of provinces under the judicial administration of a Proconsul (
anthypatos). The provinces continued to exist under the
themes until the second half of the 9th century. ==Organisation==