Complex sentence: It was an active Air Force base from the 1940s throughout the 1960s, but it always had a significant Reserve and National Guard presence, and it became a wholly reserve facility in the 1980s.
Split into simpler sentences: It was an active Air Force base from the 1940s throughout the 1960s, but it always had a significant Reserve and National Guard presence. It became a wholly reserve facility in the 1980s.