Valens

Valens was named co-emperor in 364 by his elder brother Valentinian I, who split the empire and gave him the east after an unremarkable military career. He put down the usurper Procopius in 366 after hesitating, then fought the Goths across the Danube in 367 and 369. The following years found him managing threats along the eastern frontier - Persia in Armenia, raids by Saracens and Isaurians - while at home he built the Aqueduct of Valens in Constantinople, longer than all of Rome's combined. A capable administrator who eased the tax burden, he was also indecisive, suspicious, and prone to treason trials that darkened his name. In 376 a mishandled Gothic resettlement sparked war in the Balkans. Valens marched west to meet them but failed to coordinate with his nephew Gratian; poor tactics at Adrianople on 9 August 378 killed him and shattered his army, opening the frontier in a way that stunned the Roman world.