Theodosius convened the council in Constantinople, which reaffirmed and developed Nicene doctrine and enhanced the prestige of the Constantinopolitan see—helping align eastern administration and ecclesiastical authority around the imperial capital.
A peace settlement ended the Gothic War (376–382) by incorporating Goths as foederati within imperial territory in return for military service. This was a key administrative-military arrangement in the eastern Balkans under Theodosius.
Theodosius defeated the western usurper Eugenius (backed by Arbogast) at the Battle of the Frigidus, briefly reuniting imperial authority under one ruler—an important prelude to the post-395 administrative separation under his heirs.
After the death of Valens at Adrianople (378), Gratian elevated Theodosius as Augustus to stabilize the eastern provinces and manage the Gothic crisis—creating a formal East/West division of imperial responsibilities.
Theodosius I and the Administrative Division of the Roman Empire (379–395 CE)
