The Office of Magister Militum in the 4th Century CE: A Study into the Political and Military History of the Later Roman Empire

Abstract

The magistri militum were the highest-ranking generals of the late Roman imperial army. Emperor Constantine I created this office in the early part of the fourth century with the intention of reducing the chance that generals would threaten the reigns of his sons and dynastic heirs. This was initially a success, and the magistri militum competently served the whims of the emperors for many decades. They commanded the imperial armies in war, they were involved in asserting the religious will of the emperors, and their schemes were limited to low-level politicking.

Over time, however, the magistri began to resist the dominance of the emperors, and this thesis will seek to explore how the role of the magistri changed through certain decisive moments over the course of the late fourth century. These instances included when the magister Merobaudes raised a four-year old child as a puppet emperor under his control, or when Arbogast refused an order of dismissal from the same emperor, now an adult. The final decisive moment of the fourth century was Stilicho’s appointment as guardian and protector of the emperor Honorius. These events dramatically changed the political sphere of the western Empire, which would continue to be dominated by generals until the dissolution of imperial control in western Europe. This phenomenon will be compared to different but concurrent developments in the eastern Empire, which contrastingly resulted in the dilution of military power and instead the supremacy of civil officials.

To further develop our understanding of the office of magister militum, this thesis will also conduct a prosopographical study. This will look at the religious beliefs of the magistri, the career path that lead an ambitious man to this office, as well as the ethnic identity of the magistri. The conclusions drawn from this study will show that the most potent magistri shared certain important traits that made them predisposed to seeking and achieving this massive degree of power.