Life in Britain after the Romans: 5th–7th Century Changes

1130 depiction of Saxons, Jutes, and Angles crossing the sea to Britain

Britain Abandoned: The Unravelling of Roman Rule (409–410)

The collapse of Roman Britain around 409–410 A.D. marked a profound turning point. By the early fifth century, the familiar rhythms of Roman life had largely ended: towns dwindled or emptied for centuries, coinage fell out of daily use, and clothing, diets, and architecture shifted beyond recognition. The sixth-century writer Gildas remembered the change as swift and apocalyptic, recalling desperate appeals from the Britons to Roman commanders across the Channel—pleas that went unanswered.

In the winter of 406–407, barbarian groups crossed the Rhine, and Roman units in Britain proclaimed one of their generals, Constantine (the usurper Constantine III), emperor. Around 409, Constantine drew most of the provincial field army to Gaul. The army never returned in force, and the garrisons left behind were too weak to stem fresh incursions. Some historians use the Rescript of Honorius (410)—a letter telling cities to see to their own defence—as a convenient marker of Rome’s withdrawal, though its addressees and interpretation remain debated.

With remarkable timing, raiders pressed their advantage as the legions departed. Long-familiar enemies—the Scotti of Ireland and the Picts of northern Britain—renewed their attacks, while new groups arrived in larger numbers: the Angles and Saxons from northern Germany and the Jutes from southern Denmark. The native Brittonic peoples resisted these newcomers as they had once resisted Rome, but with mixed success. Irish settlers, especially the Scotti, established footholds along the western coasts, forming several small kingdoms; among these, Dál Riata (Dalriada) became the most prominent—a seafaring Gaelic realm spanning Antrim and Argyll, built on maritime kin-networks with power centres such as Dunadd. From the late 6th century, it helped transmit the Gaelic language, law, and Christianity—anchored by Iona (founded in 563 by Columba)—and, amid contests with Northumbria and the Picts, it would ultimately feed into the emerging Kingdom of Alba.

Vortigern and the Hiring of Saxon Mercenaries

Late Roman provinces often met frontier crises by contracting foederati—allied warbands settled on land in return for military service. British tradition (first framed by Gildas) places this policy at the heart of the island’s unravelling: a “proud tyrant”—later writers identify him as Vortigern—sought quick relief from Pictish and Scotti raids by inviting Saxon fighters into Britain. When the plea to imperial authorities—the famous “Groans of the Britons”—brought no aid, local rulers turned to these newcomers as a stopgap army. Initially effective, the arrangement soon strained over rations, pay, and land. As in other late-Roman foedus breakdowns, federate leaders pressed for better terms; negotiations slipped into raiding and reprisals, and what began as a temporary alliance hardened into decades of conflict.

“The barbarians drive us to the sea; the sea drives us back to the barbarians: two forms of death await us—we are either slain or drowned.” — Gildas, De Excidio

Later narrative sources (notably Bede and the Historia Brittonum) embroider this episode with names and scenes—Hengist and Horsa, a landing in Thanet, a grant of territory that expanded into wider settlement, and a spiral from treaty to war. While these details are post-Gildas and partly legendary, they preserve a memory of how small contracted contingents could snowball into migration streams, drawing in families and followers once footholds were secured. Archaeology supports a phased process: early warband enclaves along eastern and southeastern coasts, followed by broader settlement and acculturation.

Crucially, the British response was not passive. Gildas hints at counter-offensives under Romano-British leaders (see Ambrosius Aurelianus below), and shifting alliances meant some Saxon groups fought with Britons against other raiders. Yet the strategic picture favoured the federates: the Saxon Shore forts were undermanned, imperial logistics had collapsed, and British elites could no longer guarantee pay or provisions. In that vacuum, federate commanders bargained from strength. The foedus that was meant to save the province instead reshaped it—opening the path from contracted service to Anglo-Saxon settlement and polities.

Ambrosius Aurelianus and the Long Resistance

Gildas portrays Ambrosius Aurelianus as a scion of late Roman Britain—“a gentleman whose parents, who had worn the purple, were slain in the same storms”—who gathered survivors of the provincial elite and rebuilt coordinated defence after the first Saxon shocks. Rather than a single climactic campaign, Gildas implies a protracted counter-offensive: musters of mixed Romano-British and Brittonic warbands, fortified hilltops reoccupied, fieldworks such as the Wansdyke maintained or renewed, and mobile raiding aimed at cutting federate supply and isolating enclaves. These efforts did not erase Saxon footholds, but they checked expansion long enough for a new generation to mature under relative stability.

Gildas adds a tantalising chronological clue: a span of “forty-four years and one month” from the first Saxon settlements to a “final victory” at Mons Badonicus (Mount Badon), after which came a lull in major warfare in his own youth. On this basis, modern estimates place Badon roughly c. 490–515. The site remains debated—candidates include Bath (Somerset), Badbury Rings (Dorset), and other hillforts along the western Saxon frontier—suggesting a battle fought where Roman roads, river crossings, and frontier ridges converged. Whatever the exact location, Badon appears to have been decisive enough to stall Saxon advances for decades and to reassert British control across parts of the west and “Old North.”

Notably, Gildas does not name the British commander at Badon. The later Historia Brittonum (ascribed to Nennius, 9th c.) credits Arthur as dux bellorum—a war-leader coordinating multiple kings—rather than a crowned monarch. That tradition may preserve a memory of coalition warfare, in which an experienced commander (Ambrosius himself, a successor, or a composite figure later remembered as Arthur) led multi-polity forces to a rare, large-scale victory. A prudent editorial stance is to keep Arthur’s attribution cautious, foregrounding Gildas’s contemporary testimony about Ambrosius’s role, the sequence of battles, and the long peace that followed Badon—outcomes that reshaped the balance between Brittonic and Anglo-Saxon power at the turn of the sixth century.