Valentinian III

Born 2 July 419, son of Galla Placidia and Constantius III, Valentinian III descended from two imperial dynasties: great-grandson of Valentinian I and grandson of Theodosius I. He took the throne in the West at age six in 425, making him the youngest sole emperor in Western Roman history. His mother Galla Placidia and the military commander Flavius Aetius wielded the real power through decades dominated by civil wars among generals and barbarian invasions. Aetius led a coalition that turned back Attila the Hun at the Battle of the Catalaunian Plains, then Pope Leo I negotiated an end to a second Hunnic threat. Valentinian later turned on Aetius and killed him. On 16 March 455, Aetius's bodyguards assassinated Valentinian in revenge, closing one of the longest reigns in Roman history and ending the Valentinianic dynasty amid the Western Empire's final collapse.