The assignment for duty of judge advocates of the Army, Navy, Air Force, and Coast Guard shall be made upon the recommendation of the Judge Advocate General of the armed force of which they are members. The assignment for duty of judge advocates of the Marine Corps shall be made by direction of the Commandant of the Marine Corps. The Judge Advocates General, and within the Marine Corps the Staff Judge Advocate to the Commandant of the Marine Corps, or senior members of their staffs, shall make frequent inspections in the field in supervision of the administration of military justice.