Reigns of Valentinian I and Valens

In 364 Valentinian I was proclaimed emperor and appointed his brother Valens as co-emperor in the East. Valentinian concentrated on the Rhine, Britain, Africa and the middle Danube, while Valens faced the revolt of Procopius, war with the Goths and continuing pressure from Persia.

The division allowed each emperor to respond to regional threats, but it also exposed differences in military resources and political judgement. After Valentinian’s death, the admission and mistreatment of Gothic refugees south of the Danube produced open revolt in the eastern provinces.

Valens’s decision to engage before western reinforcements arrived culminated in the Roman defeat at Adrianople in 378. The period links frontier management, imperial partnership and the changing relationship between Roman armies and migrant peoples.