Emperor also harkened back to the Roman Republic title of Imperator, as a magistrate who exercised Imperium or command, especially over an army.

[3] Emperor also harkened back to the Roman Republic title of Imperator, a magistrate who exercised Imperium or command, especially over an army.

After an especially great victory, an army's troops in the field would proclaim their commander imperator, an acclamation necessary for a general to apply to the Senate for a triumph.

Napoleon's reign lasted until 22 June 1815, when he was defeated at the Battle of Waterloo, exiled, and imprisoned on the island of Saint Helena, where he died on 5 May 1821.

His reign would nominally continue until 4 September 1870, as he was officially deposed after his defeat and capture at the Battle of Sedan during the Franco-Prussian War.