emperor [Lat. imperator = one holding supreme power, especially applied to generals], the sovereign head of an empire. In the Roman republic the term imperator referred to the chief military commander and was used only on the battlefield. It was first used continuously by Julius Caesar and was retained by his successor Augustus. It was then adopted by all succeeding Roman rulers as an official title. An emperor continuously ruled over the eastern segment of the Roman Empire, which became known as the Byzantine Empire, until the 15th cent. In the West, after the fall of the empire, the title was revived with the crowning of Charlemagne (800). Eventually the territory reigned over by the successors of Charlemagne became known as the Holy Roman Empire, which lasted until 1806. In 1721 the Russian czar Peter I adopted the title emperor, and his example was followed in the 19th cent. by the monarchs in Austria, France, Germany, and Great Britain (Indian Empire, 1877–1947). The title was also used by several rulers in the Americas—in Brazil from 1822 to 1889; in Mexico by Agustín de Iturbide and Maximilian; and in Haiti by Jean Jacques Dessalines and Henri Christophe. In a general sense the title has been used to describe a non-European ruler of considerable territory, e.g., the emperor of Japan and the emperor of Ethiopia. See also imperialism.
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