Wednesday, September 2, 2020

Departure of Rome from Britain

By E S Moxon

In the 4th Century the senior administration of Britain sat in Gaul. Military command had become regionalised with whoever sat over the Eastern Empire based in Constantinople and the Western Empire was ruled from Rome. Meanwhile the Christian church was gaining power and, depending on the religious leanings of who sat on the throne, persecutions were weighted against Pagans (including the old Roman pantheon of gods) or Christians.

The start of the demise of Roman rule in Britain isn’t easy to pinpoint, however it could have begun with the death of Constantine in AD337. For three months there was no rule in Britain while his 3 sons (Constantine II, Constans and Constantius II) squabbled over who would rule what and where. A military revolt arose in Constantinople refusing any successor but a son of Constantine and other members of the Imperial family were murdered to ensure this. For Britain, little changed as Constantine II emerged as Senior Augustus in control of Britain, Gaul and Spain.

Emperor Constantius II on Amethyst

This was not enough for Constantine II, who launched a failed attack on Constans’ domain in Italy during AD340. Then when Constans was killed by conspirators in AD350, a Germanic mercenary named Magnetius was proclaimed Augustus. Using frontier reinforcement troops in Britain (leaving these posts lacking in defence), Magnetius challenged Constantius II (Augustus of the East in Constantinople) and was victorious. Magnetius ruled for three years, allowing Pagan worship in Britain, until his defeat in Gaul at the hands of Constantius II.

This allowed Constantius to declare himself sole Augustus of the entire Roman Empire, ruling both eastern and western frontiers. He reintroduced the death penalty for Pagan worship or sacrifice. The religious barometer swung back to Christianity once more. Sympathisers of Magnetius were punished severely and many villas became abandoned as high officials fled. These sumptuous places became home to squatters or servants’ families left behind.

City of Constantinople 

The religious barometer swung back to Paganism around AD355 when Constantius gave his young cousin Julian rule of Britain and Gaul. The new Caesar was passionate about literature and the ancient Roman gods. There is no mention of Christians being persecuted during this time, so we must assume that both old and new faiths co-existed and were freely worshipped. It seems Julian was perhaps an idealist, attempting to embrace the past and the future.

Admired by his troops for being an extraordinary general, he quickly drew disfavour from Constantius who resented his younger cousin’s popularity. The family quarrel led to a military revolt against Constantius, who died before the cousins could meet in battle and the troops declared Julian sole Augustus. In response to this, possibly feeling brave, Julian came out as a devoted Pagan and restored Roman observances of the old pantheon.

Aberlemno Pictish Cross

By AD367 a quarter of the Roman army was Germanic in origin (and therefore most likely Pagan). Britain was now being harassed from all sides by the Picts, Saxons, Scotts and Attacotti. To compound things, troubles in the Eastern Empire meant garrisons from Britain were removed to assist. Once again this depleted the frontier defences of Britain during a period of intense attacks by several foes. These foes were opportunists and seized their moment. The Franks and Saxons invaded Gaul, while Picts, Scotts and Attacotti attacked Britain, causing Roman officials to abandon their posts.

Over the next twenty-five years Rome battled the mercenaries, attempting to regain control and restore Roman rule in its splintered Western Empire. Valentian ruled the Imperial family until his hanging in AD391, but lost control of Britain with the arrival of Magnus Maximus in AD383, who led a victory against the Picts and Scotts (something Rome had failed to do) and invaded Gaul, setting up a court at Trier where he was baptised Catholic. His defeat came at the hands of Theodosius in AD388 when they were defeated at Aquilea. Before his death in AD395 Theodosius ordered repairs along Hadrian’s Wall and the construction of watch-towers along the north-eastern coast. He also tried to help the Christian diocese to recover.

Hadrian's Wall

By now the Pennine and Welsh forts were abandoned. Britain must have been a bleak and savage place, with Germanic mercenaries billeted in towns and control being snatched repeatedly from the hands of the Imperial Roman family. In AD392 Eugenius, Arbogastes and Flavianus arrived on the scene. Theodosius battled Eugenius in AD394 and won, no doubt refusing to allow usurpers to undo all his hard work on frontier fortification. As a result of Eugenius’ defeat, Arbogastes and Flavianus committed suicide.

The descendants of Theodosius, Arcadius and Honorius, were both Augustus, with the latter ruling into the beginning of the 5th Century. What then of the fate of Britain? After such turmoil, could Rome hold onto her and rule successfully? It appeared so for a while at least. Following the demise of Theodosius in AD395, his sons took over. In AD398 they repelled a joint Pict/Scott invasion with their western troops, who were mostly Germanic mercenaries, those called ‘foederati’. These barbarian troops were at the forefront of guarding Britain, along Hadrian’s Wall and the east coast shore forts. However, despite their military successes, Fate frowned on Rome.

Stilicho negotiating with Goths

In AD401 the Goth, Alaric came over the Alps and had Rome securely in his sights. Stilicho, a ‘magister militum’ who had married a niece of Thoedosius, wintered in the Danube desperately trying to recruit additional barbarian troops. This was to no avail. With almost no financial assistance from Honorius it had been hard to raise men to the cause. The barbarian army revolted against Stilicho and crossed back over the Rhine.

Meanwhile in Britain, they had had revolts of their own. The army made a Romano-Briton named ‘Gratian’ their leader, who was swiftly disposed of and replaced with Constantine III who moved to Gaul before the barbarian Germanic army of Stilicho could cross the Channel. The barbarians turned south. By AD407 Constantine III had taken back Gaul with his son and took Britain in AD408, forcing Honorius to accept Britain as a prefecture under Gaul in AD409. But there was more upheaval to come.

Alaric and his Goth army sacked Rome in AD410. In a panic to raise troops, all garrisons from Britain were recalled. This caused a civil war to erupt as several sought the title of Augustus and were forced to raise their own armies to fend off barbarian attacks. They ejected Roman officials from their offices and by AD413 no attempts had been made by Rome to bring Britain back under the rule of Honorius. Rome had certainly fallen, at the very least, in Britain.


“Roman Britain” by Martin Millett (English Heritage)

“Oxford Illustrated History of Roman Britain” by Peter Salway

“Britain AD” by Francis Pryor


E S MOXON has had a lifelong passion for history and writing. A childhood filled with family visits to ancient burial sites and stone circles fuelled her imagination. Inspired by classic medieval tales and Norse sagas, Elaine imagined herself inhabiting these Dark Ages and exploring the landscapes in her mind and continues to do so through her novels.

Tales of the Wulfsuna


  1. Yes, in some ways one might describe the process as the 'expulsion' of Rome from Britain, though it's fairly clear that some of those who ruled Britain after the absence of Rome still hoped to be supported by Rome. When that did not happen, the rule of Britain became fragmented by around 450 AD - but how that happened and how fast is not clear at all.

    1. Yes, all these unknowns really drive my fascination for this period. We're still finding fragments of that time, hoping they shed miniscule shafts of light on this Dark Age. Thanks for the comment Derek!

  2. Great article, however, Rome is fairly stationary, Urbi et Orbi.


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