Complex sentence: Leavitt served as commander of the 333d Fighter Squadron at Seymour Johnson Air Force Base, North Carolina before being appointed Commander, 4th Fighter Wing, at the same base in June 2012.
Split into simpler sentences: Leavitt served as commander of the 333d Fighter Squadron at Seymour Johnson Air Force Base, North Carolina. She was appointed Commander, 4th Fighter Wing, at the same base in June 2012.