Magnus Maximus
In the summer of 383 Gratian was again at war with the Alamanni in Raetia. Gratian alienated the army by his favouritism towards his Alan deserters whom he made his body-guard and to whom he gave military commands. This favouritism of former enemies and the paganism of the Alans angered his Christian army. By 383 the Roman general Magnus Maximus had raised the standard of revolt in Britain and invaded Gaul with a large army. when a rebellion broke out in Britain under Magnus Maximus (), the commander of the Roman troops there. Magnus Maximus, who had served under the "comes" Theodosius and had won a victory over the Picts in 382, was proclaimed "augustus" and crossed the channel, encamping near Paris. There, his forces encountered Gratian, but much of the latter's army defected to this usurper, forcing Gratian to flee.