The Edict of Thessalonica, issued by three Roman emperors in 380 AD, marked the beginning of Christendom.
The persecution of the early Christian Church under the Roman Empire had been temporarily halted for the first time in the early fourth century, with the emperors Constantine the Great and Licinius I, who respectively led the western and eastern parts of the empire, issuing the Edict of Milan in 313. The edict determined that Christians ought to be treated with benevolence within the Roman Empire. Constantine’s successors, Constantius II and Julian the Apostate, favored paganism, Arianism, and Judaism over Christianity, however.
The Constantinian dynasty ended in 364 AD, to be succeeded by the Valentinians. The Valentinians would rule the Western Roman empire until 392 and the East until 378. The first two emperors of this dynasty, Valentinian I and Valens, were either impartial towards Christianity or favorable towards the Arians.
In 367 things started to change radically for Christianity in the Roman Empire. Gratian, son of Valentinian I, succeeded Valens as Roman emperor. Gratian refused participation in the imperial cult and removed some pagan idols from public spaces in Rome. He appointed the Christian bishop Ambrose as his chief advisor. ...
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