The United States Army Rangers are U.S. Army personnel who have served in any unit which has held the official designation of "Ranger". The term is commonly used to include graduates of the Ranger School, even if they have never served in a "Ranger" unit, because Army regulations and special qualification identifier (SQI) codes provide that the only requirement to earn the "Title: Ranger" is that a soldier "must successfully complete the appropriate training at the Infantry School."
In a broader and less formal sense, the term "ranger" has been used, officially and unofficially, in North America since the 17th century, to describe specialized light infantry in small, independent units—usually companies. The first units to be officially designated Rangers were companies recruited in the New England Colonies to fight against Native Americans in King Philip's War. Following that time, the term became more common in official usage, during the French and Indian Wars of the 18th century. The U.S. military has had "Ranger" companies since the American Revolutionary War. British Army units designated as "Rangers" have often also had historical links of some kind to British North America.
