On This Day in Ancient History - January 19 -
Under Emperor Valentinian I, Theodosius was stripped of military command in Moesia and retired to Spain. His father had been executed, possibly for interceding on behalf of his son. Despite such inasupicious beginnings, Theodosius, with his 8-year-old son installed in name as ruler of the Western Empire, was the last emperor to rule the entire Roman Empire in fact.
Read about how Theodosius came to power in the Accession of Theodosius I.
For Moesia, see Map of the eastern provinces of the Roman Empire. Moesia is the province east of Pannonia, about 45N.