person who is enlisted in a branch of the armed force
United States Armed Forces oath of enlistment Upon enlisting in the United States Armed Forces, each person enlisting in an armed force (whether a soldier, sailor, coast guardsman, airman, or Marine) takes an oath of enlistment required by federal statute in 10 U.S.C. § 502. That section provides the text of the oath and sets out who may administer the oath:
Lieutenant colonel (United States) In the United States Army, U.S. Marine Corps, and U.S. Air Force, a lieutenant colonel is a field grade military officer rank just above the rank of major and just below the rank of colonel. It is equivalent to the naval rank of commander in the other uniformed services.