The longest lived of Constantine the Great's sons and successors, he ruled until 361 A.D. Upon Constantine's death, Constantius received the entire eastern empire as his inheritance. Soon after he added Thrace to his empire and as his brothers were killed, he annexed their territories. When he defeated the Western usurper Magnentius he was master of the entire empire. Although he started campaigning along the Danube, war with Persia forced his return to the East. Shortly after, he received news that Julian II had been proclaimed Augustus against him. Constantius died on his way to fight this new usurper and Julian II became ruler of the Roman Empire.