The Roman garrison on Hadrian's Wall rebels in the winter of 367, and allows Picts from Caledonia to enter Britannia.

Simultaneously, Attacotti, Scotti from Hibernia, and Saxons from Germania, land in coordinated and pre-arranged waves on the island's midwestern and southeastern borders, respectively.

Franks and Saxons also land in northern Gaul.

These warbands manage to overwhelm nearly all of the loyal Roman outposts and settlements.

The entire western and northern areas of Britannia are overwhelmed, the cities sacked and the civilian Romano-British murdered, raped, or enslaved.

Nectaridus, the Count of the Saxon Shore, is killed and the dux britanniarum, Fullofaudes, is either besieged or captured, the remaining loyal army units staying garrisoned inside southeastern cities.

The areani or local agents whom the Romans pay to provide intelligence on barbarian movements seem to have betrayed their paymasters for bribes, making the attacks completely unexpected.

Deserting soldiers and escaped slaves roam the countryside and turn to robbery to support themselves.

Although the chaos is widespread and initially concerted, the aims of the rebels are simply personal enrichment and they work as small bands rather than larger armies.

Emperor Valentinian, campaigning against the Alamanni at the time, is unable to respond personally.

A series of commanders to act in his stead are chosen but swiftly recalled.

The first was Severus, the emperor's comes domesticorum, soon replaced by Jovinus, the magister equitum; rumors of disasters dog them, however, and almost fifteen months before a capable replacement is sent.