When this movie came out, we loved it because it matched our thinking. The story wasn’t something we had to be sold on. Our biggest threat was the Soviet Union and the spread of communism. We were young, and the movie was about young people fighting the invasion. And what did young people do for fun in those days? We went to the movies. Perfect recipe for success at the box office.
The movie is on YT free (with ads) if anyone wants to watch it:
https://www.youtube.com/watch?v=t7V0IZ51wDg
It’s been 40 years since I last watched it.