Theodosius I

Theodosius I (Latin: Theodosius, Ancient Greek: Θεοδόσιος Theodósios; 11 January 347 – 17 January 395), also known as Theodosius the Great, was Roman emperor from 379 to 395. He won two civil wars and was instrumental in establishing the Nicene Creed as the orthodox doctrine for Nicene Christianity. Theodosius was the last emperor to rule the entire Roman Empire. After his death, his sons Arcadius and Honorius ruled from separate courts in the east and the west, continuing the late Roman practice of rule by multiple emperors. He ended the Gothic War (376–382), but did so on terms disadvantageous to the empire, with the Goths remaining politically autonomous within Roman territory, albeit as nominal allies.

Born in Hispania, Theodosius was the son of a high-ranking general of the same name, Theodosius the Elder, under whose guidance he rose through the ranks of the Roman army. Theodosius held independent command in Moesia in 374, where he had some success against the invading Sarmatians. Not long afterwards, he was forced into retirement, and his father was executed under obscure circumstances. Theodosius soon regained his position following a series of intrigues and executions at Emperor Gratian's court. In 379, after the eastern Roman emperor Valens was killed at the Battle of Adrianople against the Goths, Gratian appointed Theodosius as a successor with orders to take charge of the military emergency. The new emperor's resources and depleted armies were not sufficient to drive the invaders out; in 382 the Goths were allowed to settle south of the Danube as autonomous allies of the empire. In 386, Theodosius signed a treaty with the Sasanian Empire which partitioned the long-disputed Kingdom of Armenia and secured a durable peace between the two powers.

Theodosius was a strong adherent of the Christian doctrine of consubstantiality and an opponent of Arianism. He convened a council of bishops at the First Council of Constantinople in 381, which confirmed the former as orthodoxy and the latter as a heresy. Although Theodosius interfered little in the functioning of traditional pagan cults and appointed non-Christians to high offices, he did not prevent or punish Christians for the demolition of several pagan temples of classical antiquity such as the Serapeum of Alexandria.