The Tetrarchy, inaugurated in 285 AD by Emperor Diocletian, had been instituted mainly with the intent of mitigating successions tribulations such as those that had plagued the third century. But the system began to breakdown in 306 when Emperor Constantius Chlorus died in Eboracum (York, UK) and the army serving under him illegitimately designated his son Constantine I as his successor. The latter emerged, 19 years later, as the last man standing following a series of deadly rivalries between several determined candidates to the purple cloak. By then, the well envisioned experiment of the Tetrarchy had become a distant memory and Constantine I ruled the Empire as sole emperor from 325 until his death in 337.

During this crucial 12-year period, important administrative reforms were undertaken, and the Roman army experienced a major reorganization in its structure and composition. As the Empire was recovering its former military might, Christianity officially became the state religion.

Modern bronze statue of Constantine I in York, England, near the spot where he was proclaimed Augustus in 306 (Chabe01 / CC BY-SA 4.0)

Constanine’s Reforms
The last period of Constantine I’s reign was far from being inactive. In the military field, the concept of the mobile army initiated by Emperor Gallienus 60 years earlier was finally instituted. Part of the frontier troops were permanently grouped into mobile units stationed in strategic locations within the Empire. The long-term effects of this reorganization for the defence of the Empire are not unanimous among modern historians; but most agree that in the short-term it was very useful for Constantine I during the military campaigns that followed against the Barbarians. In fact, in 328, the Emperor inflicted a severe defeat on the Alemanni on the Rhine and then carried out a large-scale victorious campaign against the Goths on the Danube. In 334, he massively attacked the Sarmatians and temporarily brought back under Roman control most of Dacia (modern Romania), evacuated by Emperor Aurelian in 275.

Although proven a good military leader, Constantine I was not as capable as an administrator, but he had the wisdom to surround himself with competent and loyal advisors who ruled the Empire with and through him. Under Constantine I, within the now theocratic State, imperial protocol was heightened, and the centralization of power was further accentuated.

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Mario Bartolini has a master’s degree in political history from the Université de Sherbrooke, Canada, and a second master’s degree in war studies, obtained at the Royal Military College of Canada. He is the author of Roman Emperors: A Guide to the Men Who Ruled the Empire

Top Image: Battle of the Milvian Bridge between the Roman Emperors Constantine I and Maxentius on 28 October 312 AD by Giulio Romano ( 1520-24). Vatican City (Public Domain)