A rill instructor (or Drill Sergeant) is a non-commissioned officer in the armed forces with specific duties that vary by country. In the U.S. armed forces, they are assigned the duty of initiating new recruits entering the military into the customs and practices of military life. In the U.S. (in the Air Force, particularly) they may also be known as military training instructors. Outside of the U.S., they are assigned the duty of instructing recruits in drill commands only.