Complex sentence: At the time, the Army leadership felt that the U.S. Air Force was not doing enough to support ground forces, and due to the Key West Agreement, the Army could not field its own ground attack fixed-wing aircraft.
Split into simpler sentences: At the time the army leadership felt that the U.S. Air Force was not doing enough to support ground forces. Due to the Key West Agreement, the Army could not field its own ground attack fixed-wing aircraft.