Constantius II ruled the Roman Empire from 337 to 361. He was the second son of Constantine the Great and Fausta. Constantius was a devout follower of Arianism Christianity. Ruling for 24 years, he was the longest reigning son of Constantine and therefore, arguably, the most successful.
He became Augustus together with his brothers, Constantine II and Constans on September of 337 after the death of his father. 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' 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. The two remaining brothers maintained an uneasy peace with each other until, in 350, Constans was overthrown and assassinated by the usurper Magnentius. Unwilling to accept Magnentius as co-ruler, Constantius waged a civil war against the usurper, defeating him and leaving Constantius as sole ruler of the empire.
