Theodosius I (Theodosius the Great)

Flavius Theodosius, known as Theodosius the Great, was a formidable Roman military commander from Hispania who became the final emperor to hold undisputed sovereign dominion over both the Eastern and Western halves of the Roman Empire. Summoned to the throne by Emperor Gratian following the catastrophic Roman annihilation at the Battle of Adrianople (378 CE), Theodosius checked the rampaging Visigoths and stabilized the imperial frontiers.

Theodosius dramatically reshaped Western religious and political history. In 380 CE, he issued the Edict of Thessalonica, decreeing Nicene Trinitarian Christianity to be the sole authorized state religion of the Roman Empire and effectively ending centuries of official paganism and Arian schism. He convened the First Council of Constantinople in 381 CE and banned pagan sacrifices and the ancient Olympic Games. Upon his death in Milan in 395 CE, the Roman Empire was permanently partitioned between his two sons, Arcadius and Honorius, never again to be united under a single sovereign.