Britannia

Conquered by Emperor Claudius from 43 CE onward, fulfilling an ambition Julius Caesar had failed to complete a century earlier with his two expeditions of 55 and 54 BCE. Hadrian's Wall, begun in 122 CE, marked the empire's practical limit against the unconquered north. Roman military strength drained away through the late 4th century -- the usurper Magnus Maximus stripped troops for a continental campaign in 383, and the last legions were formally withdrawn by 410, when Emperor Honorius told British cities to look to their own defence. Boudica's revolt of 60-61 CE, sparked by the brutal treatment of her Iceni kingdom after her husband's death, briefly threatened to destroy Roman Britain altogether -- her forces burned Londinium, Camulodunum, and Verulamium to the ground before being crushed, at a cost historians estimate in the tens of thousands of lives. Londinium itself grew from a minor river crossing into the province's largest city and effective capital, its docks handling trade across the whole North Sea and Channel network. The province never fully pacified the far north -- Hadrian's Wall and later the shorter-lived Antonine Wall represented successive attempts to fix a defensible frontier against the Picts and other unconquered peoples of Caledonia. By the late 4th century, repeated barbarian incursions (the so-called "Barbarian Conspiracy" of 367 combined Pictish, Scoti, and Saxon raiders in a coordinated assault) had badly weakened the province even before Rome's final withdrawal, leaving a fragmented and increasingly Anglo-Saxon-settled land in its wake.

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