Excerpts from Books and Wikipedia
The threat of Persian invasion, was diminishing. He declared in 380 that Nicene Christianity was the one true faith. "Theodosius had declared all Christians to be one, but the eastern and western halves of his catholic church were beginning to pull apart." [Bauer: Medieval World, p. 56-9] Last emperor to rule over both West and East Roman Empire; "On accepting his elevation, he campaigned against Goths and other barbarians who had invaded the Empire. . . . By treaty, which followed his indecisive victory at the end of the Gothic War, they were established as foederati, autonomous allies of the Empire, south of the Danube, in Illyricum, within the Empire's borders. . . . He issued decrees that effectively made Nicene Christianity the official state church of the Roman Empire. He neither prevented nor punished the destruction of prominent Hellenistic temples of classical antiquity, including the Temple of Apollo in Delphi and the Serapeum in Alexandria. He dissolved the Order of the Vestal Virgins in Rome. In 393, he banned the pagan rituals of the Olympics in Ancient Greece. " [Wikipedia]