Emperor Theodosius I proclaims Nicene Christianity the state religion of the Roman Empire.
Date given in the Julian calendar.
The Goths, many of whom had crossed the Danube fleeing the Huns, crush a Roman army and kill Emperor Valens.
After the death of Theodosius I, the empire is divided between his two sons into Western and Eastern halves, never to be reunited.
Visigoths under Alaric I enter and sack Rome, the first time in about 800 years the city had fallen to a foreign enemy.
Emperor Constantine I dedicates Constantinople as the new capital of the Roman Empire.
The first ecumenical council of Christianity, convened by Constantine, condemns Arianism and formulates the Nicene Creed.
Emperors Constantine and Licinius agree on religious toleration, ending the persecution of Christians in the Roman Empire.