383–388 AD – Magnus Maximus

What Happened

In AD 383, a powerful and ambitious Roman general named Magnus Maximus, who was commanding the troops in Britain, launched a major rebellion against the legitimate Western Roman Emperor, Gratian. Maximus, a Spaniard by birth, had served with distinction in Britain under Count Theodosius during the Great Barbarian Conspiracy (AD 367–368) and had subsequently risen to the rank of Comes Britanniarum (Count of the Britains).

Maximus's usurpation was likely driven by the growing unpopularity of Gratian among the western legions, who resented his favouritism towards Alan mercenaries and his perceived neglect of the traditional Roman military establishment. Maximus, capitalizing on this discontent, was proclaimed emperor by his troops in Britain.

To secure his claim, Maximus stripped Britain of a significant portion of its garrison, taking the legions and auxiliary units across the English Channel to Gaul. He rapidly advanced against Gratian, whose own troops deserted him near Paris. Gratian fled but was captured and assassinated at Lugdunum (Lyon) by Maximus's Magister Equitum (Master of the Horse), Andragathius.

Maximus established his capital at Augusta Treverorum (Trier) and successfully ruled Britain, Gaul, and Hispania for five years. He was a staunch defender of Nicene Christianity and famously executed the ascetic Priscillian for heresy, the first time a Christian was put to death by the state for religious reasons. He also negotiated a fragile peace with the Eastern Roman Emperor, Theodosius I (the son of his former commander), who reluctantly recognized him as a legitimate co-emperor in the west, provided he did not attack the young Valentinian II in Italy.

However, in AD 387, Maximus broke this agreement and invaded Italy, forcing Valentinian II to flee to the east. Theodosius I, now compelled to act, marched west with a massive army. In AD 388, Theodosius decisively defeated Maximus's forces at the Battle of the Save (in modern-day Croatia) and subsequently captured and executed Maximus at Aquileia.

Why It Mattered

The usurpation of Magnus Maximus (AD 383–388) was a critical event in the late history of Roman Britain. By withdrawing a large number of troops to fight his civil war on the continent, Maximus significantly weakened the island's defences. This withdrawal is often seen as the beginning of the end of Roman military control in Britain, as many of these troops never returned.

The vulnerability of the province following Maximus's departure allowed the Picts, Scots, and Saxons to renew their devastating raids. The Welsh legend of Macsen Wledig (the Welsh name for Maximus) portrays him as a founding figure who left Britain to conquer Rome, settling his British troops in Armorica (Brittany) and establishing a lasting connection between the two regions. While the historical accuracy of this legend is debated, it reflects the profound impact of his departure on the collective memory of the Britons.

Maximus's reign also highlighted the growing religious intolerance within the empire. His execution of Priscillian set a dangerous precedent for state-sponsored religious persecution, demonstrating his willingness to use extreme measures to enforce orthodoxy and secure the support of the powerful Nicene bishops.

Human Perspective

For the Roman soldiers in Britain, the proclamation of Magnus Maximus was a familiar pattern of military usurpation. They had served under him and respected his leadership, and their decision to follow him to Gaul was a gamble for power and wealth. The subsequent civil war and the final defeat at Aquileia must have been a devastating blow, resulting in the loss of many experienced troops and leaving their families in Britain vulnerable to barbarian attacks.

For the Romano-British population, the departure of Maximus and his army was a profound trauma. The stripping of the garrison removed their primary source of protection, exposing them to the renewed violence of the Picts, Scots, and Saxons. The legend of Macsen Wledig, while romanticizing his conquests, also reflects the sense of abandonment and the enduring legacy of his usurpation. The events of 383–388 demonstrated that the security of Britain was increasingly subordinated to the ambitions of its military commanders and the chaotic politics of the wider empire, fracturing Roman Empire.