History of Europe
In 395 Theodosius I, who had made Christianity the official religion of the Roman Empire, would be the last emperor to preside over a united Roman Empire. The empire was split into two halves: the Western Roman Empire centred in Ravenna, and the Eastern Roman Empire (later to be referred to as the Byzantine Empire) centred in Constantinople. The Roman Empire was repeatedly attacked by Hunnic, Germanic, Slavic and other “barbarian” tribes (see: Migration Period), and in 476 finally the Western part fell to the Heruli chieftain Odoacer.
Roman emperor
This line of Roman emperors was actually generally Germanic rather than Roman, but maintained their Roman-ness as a matter of principle. These emperors used a variety of titles (most frequently ""Imperator Augustus"") before finally settling on "Imperator Romanus Electus" ("Elected Roman Emperor"). Historians customarily assign them the title "Holy Roman Emperor", which has a basis in actual historical usage, and treat their "Holy Roman Empire" as a separate institution. To Latin Catholics of the time, the Pope was the temporal authority as well as spiritual authority, and as Bishop of Rome he was recognized as having the power to anoint or crown a new Roman emperor. The last man to be crowned by the pope (although in Bologna, not Rome) was Charles V. All his successors bore only a title of "Elected Roman Emperor".