Gratian

Valentinian I elevated his eight-year-old son Gratian to the rank of Augustus (co-emperor) at Amiens. This was intended to secure the succession and stabilize the Western Roman Empire. Gratian was placed under the tutelage of experienced officials.

Gratian's generals led Roman forces to a decisive victory over the Alamanni at Argentovaria (modern Colmar, France). The battle crushed the Alamanni threat to Gaul. Gratian personally led the pursuit of the defeated tribes, earning military prestige.

Under the influence of Bishop Ambrose of Milan, Gratian refused to wear the robes of the Pontifex Maximus, the traditional title of the Roman emperor as chief priest of the pagan state religion. He also removed the Altar of Victory from the Roman Senate, symbolizing the end of official paganism.

The Roman general Magnus Maximus was proclaimed emperor by his troops in Britain. He invaded Gaul and confronted Gratian near Paris. Gratian's army deserted him, and he fled to Lugdunum (Lyon), where he was captured and executed by Maximus's forces.