ANGARIA, the term used to denote the postal system adopted by the Roman imperial government from the ancient Persians, among whom, according to Xenophon, it was established by Cyrus the Great. The word is derived from the Greek form of a word, originally Babylonian, meaning "mounted courier." Couriers on horseback were posted at certain stages along the chief roads of the empire, for the transmission of royal dispatches by night and day in all weathers. In the Roman system the supply of horses and their maintenance was a compulsory duty from which the emperor alone could grant exemption. The word came to mean generally "compulsory service." So angaria, in mediaeval Latin, and the rare English derivative "angariation," came to mean any service which was forcibly demanded, and oppression in general. See Xenophon, Cyrop., viii. 6; Herodotus viii. 98.