When an officer or enlisted person of the United States Army, United States Navy, or United States Air Force, detailed by the Department of the Army, the Department of the Navy, or the Department of the Air Force for service with the National Guard or Naval Militia, is detailed by the Governor for special duty or requested to perform any duty involving travel not specially directed by the Department of the Army, the Department of the Navy, or the Department of the Air Force, the officer or enlisted person shall be allowed their actual traveling expenses, but no per diem.