End of Roman rule in Britain

Part of a series on the
History of the British Isles
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The end of Roman rule in Britain was the transition from Roman Britain to post-Roman Britain. Roman rule ended in different parts of Britain at different times, and under different circumstances.

In 383, the usurper Magnus Maximus withdrew troops from northern and western Britain, probably leaving local warlords in charge. Around 410, the Romano-British expelled the magistrates of the usurper Constantine III, ostensibly in response to his failures to use the Roman garrison he had stripped from Britain to protect the island. Roman Emperor Honorius replied to a request for assistance with the Rescript of Honorius, telling the Roman cities to see to their own defence, a tacit acceptance of temporary British self-government. Honorius was fighting a large-scale war in Italy against the Visigoths under their leader Alaric, with Rome itself under siege. No forces could be spared to protect distant Britain. Though it is likely that Honorius expected to regain control over the provinces soon, by the mid-6th century Procopius recognised that Roman control of Britannia was entirely lost.

Background

By the early 5th century, the Roman Empire could no longer defend itself against either internal rebellion or the external threat posed by Germanic tribes expanding in Western Europe. This situation and its consequences governed the eventual permanence of Britain's detachment from the rest of the Empire.

In the late 4th century, the empire was controlled by members of a dynasty that included the Emperor Theodosius I. This family retained political power within itself and formed alliances by intermarriage with other dynasties, at the same time engaging in internecine power struggles and fighting off outside contenders (called "usurpers") attempting to replace the ruling dynasty with one of their own. These internal machinations drained the Empire of both military and civilian resources. Many thousands of soldiers were lost in battling attempted coups by figures such as Firmus, Magnus Maximus and Eugenius.

The Empire's historical relationship with Germanic tribes was sometimes hostile, at other times cooperative, but ultimately fatal, as it was unable to prevent those tribes from assuming a dominant role in the relationship. By the early 5th century, as a result of severe losses and depleted tax income, the Western Roman Empire's military forces were dominated by Germanic troops, and Romanised Germans played a significant role in the empire's internal politics. Various Germanic and other tribes beyond the frontiers were able to take advantage of the Empire's weakened state, both to expand into Roman territory and, in some cases, to move their entire populations into lands once considered exclusively Roman, culminating in various successful migrations from 406 onwards. The crossing of the Rhine caused intense fear in Britannia, prone as it was to being cut off from the Empire by raids on the primary communications route from Italy, to Trier to the Channel Coast. In the event, this was much more than just another raid.