The New Student's Reference Work/Valentinian II
Valentinian II, an infant four years of age, and his half-brother Gratian, a lad of 17, became joint emperors of the Western Roman empire in 375 A. D. They made Milan their residence, while the empire was at least nominally divided between them, Valentinian taking Italy and a part of Africa. Gratian died in 383, and four years later Maximus, who had commanded a Roman army in Britain, crossed the Alps into the valley of the Po and threatened Milan. The emperor and his mother Justina fled to Theodosius, emperor of the East, and besought his assistance, and. in accordance with their request Theodosius marched into Italy with an army, defeated Maximus, and again set Valentinian on the throne. He was assassinated in 392 A. D.