Mercenary
Mercenary, a professional soldier hired for service by a foreign country. Mercenaries have been used throughout history. In ancient times, the Greeks were renowned mercenaries, often used to fill Persian ranks. During the late Middle Ages, most European countries relied on mercenaries. The most formidable mercenary forces were Swiss, Scottish, and German. In Renaissance Italy the condottieri, composed of various nationalities, were hired by competing Italian princes.
With the rise of national armies in the 18th century, the use of mercenaries declined. The British, however, hired Hessians for use in the American Revolutionary War. The most renowned mercenary army of the 19th and 20th centuries is the French Foreign Legion.