Flavius Julius Constantius, known as Constantius II, was Roman emperor from 337 to 361. His reign saw constant warfare on the borders against the Sasanian Empire and Germanic peoples, while internally the Roman Empire went through repeated civil wars, court intrigues and usurpations. His religious policies inflamed domestic conflicts that would continue after his death.
Constantius was a son of Constantine the Great, who elevated him to the imperial rank of caesar on 8 November 324 and after whose death Constantius became augustus together with his brothers, Constantine II and Constans on 9 September 337. He promptly oversaw the massacre of his father-in-law, an uncle and several cousins, consolidating his hold on power. The brothers divided the empire among themselves, with Constantius receiving Greece, Thrace, the Asian provinces and Egypt in the east. For the following decade a costly and inconclusive war against Persia took most of Constantius's time and attention. In the meantime, his brothers Constantine and Constans warred over the western provinces of the empire, leaving the former dead in 340 and the latter as sole ruler of the west.