Lably
Skip to content

Magister militum

Imperial Roman military office

  • 8 min read
  • 3 chapters

Explore on Lably

ToursExplore Lably’s 3D tours

Establishment and development of the command

The office of magister militum was created in the early 4th century, most likely when the Western Roman emperor Constantine the Great defeated all other contemporary Roman emperors, which gave him control over their respective armies. Because the Praetorian Guards and their leaders, the Praetorian Prefects, had supported Constantine's enemy, Maxentius, he disbanded the Guard and deprived the Prefects of their military functions, reducing them to a purely civil office. To replace them, he created two posts: a commander of the infantry, the magister peditum ("master of foot"), and a more prestigious cavalry commander, the magister equitum ("master of horse"). These offices had precedents in the immediate imperial past, both in function and idea; the latter title had existed since republican times, as the second-in-command to a Roman dictator.

Under Constantine's successors, the titles were also established at a territorial level: magistri peditum and magistri equitum were appointed for every praetorian prefecture (per Gallias, per Italiam, per Illyricum, per Orientem), and, in addition, for Thrace and, sometimes, Africa. On occasion, the offices would be combined in a single person, then styled magister equitum et peditum or magister utriusque militiae ("master of both forces"). Overall, lower-level magistri were assigned according to circumstances, with varying numbers employed in a given area. Some were directly in command of the local mobile field army of the comitatenses, which acted as a rapid reaction force. Other magistri remained at the immediate disposal of the emperors, and by the late fourth century or early fifth century were termed in praesenti ("in the presence" of the emperor).

Over the course of the fourth century in the Western Roman Empire, the system of two imperial magistri remained largely intact, with usually one magister having paramount authority (such as Bauto or Merobaudes, the main power behind the appointment of emperor Valentinian II.) This tendency culminated in Arbogast, who inherited the position of western magister militum and used it to functionally usurp emperor Valentinian II, either killing him or driving him to suicide before appointing his own puppet emperor, Eugenius. In the west, the position (often under the title of magister utriusque militiae or MVM) remained very powerful until the formal end of the empire, and was held by Stilicho, Aetius, Ricimer, and others.

In the east, emperor Theodosius I (379–395) expanded the system of two magistri militum to include an additional three magistri. For a long time these generals were used in an ad hoc manner, being employed wherever they were needed. Eventually in the fifth century their positions became more firmly established, and there were two senior generals, who were each appointed to the office of magister militum praesentalis.

After the final partition of the Roman Empire in 395, the office continued to exist both in the Western and Eastern parts of the divided Empire. One of the most notable examples of prominence and increasing importance of that military office occurred with Marcellinus, who was magister militum in Dalmatia, acting not only as regional military commander, but also as effective governor in the entire region, from 454 to 468.

Continuation and evolution in the Byzantine Empire

The office of magister militum consequently evolved in nature and scope during the early Byzantine period.

During the reign of Emperor Justinian I (527–565), with increasing military threats and the expansion of the Byzantine Empire, the posts of the eastern generals were overhauled: the magister militum per Armeniam in the Armenian and Caucasian provinces, formerly part of the jurisdiction of the magister militum per Orientem, the magister militum per Africam in the reconquered African provinces (534), with a subordinate magister peditum, and the magister militum Spaniae (c. 562).

In the course of the 6th century, internal and external crises in the provinces often necessitated the temporary union of the supreme regional civil authority with the office of the magister militum. In the establishment of the exarchates of Ravenna and Carthage in 584, this practice found its first permanent expression. In various provinces of the Exarchate of Ravena, from Venetia to Naples, magistri militum were appointed both as local military commanders and provincial governors. For example, such was Mauricius, who was magister militum of Byzantine Venetia in 639.

After the loss of the eastern provinces to the Muslim conquest in the 640s, the surviving field armies and their commanders formed the first themata.

Sign in to keep reading

2 more chapters are free with a Lably account.

More in Ancient history

Ancient RomeRoman civilisation from the 8th century BC to the 5th century ADAncient GreeceGreek civilization from 1200 BC to 600 ADAncient EgyptCradle of civilization in North AfricaBronze AgeHistorical period (c. 3300–1200 BCE)MesopotamiaHistorical region of West AsiaAchaemenid EmpireAncient Iranian empire, 550–330 BC