Pssst. It didn't happen, which makes the whole thing silly
28 years or so ago a whole lot of people actually believed this nonsense and used it to try to scare Britain into unilateral disarmament.
Well folks, you'll be delighted to know that the Cold War is over, the bad guys lost, and the threat of nuclear war with the Muscovites is now markedly diminished. Why? Because the people that mattered were not intimidated by the scare tactics of the 80s disarmanent movement which led to this film, and the Soviet Empire collapsed trying to keep up with the West.
This film is a wonderful study in failed propaganda. Try to remind yourselves that nothing predicted and dramatized by the film actually happened. It's a little disturbing watching people call this nonsensical scare scenario "visionary" and "prophetic". It's like watching a movie about the elephants holding the world up going on a stampede -- interesting, but not to be taken seriously. Or watching a movie about the religious nut who gathered his people in the mountains of California because he thought California was going to slide into the Pacific a couple decades ago. After a month or so of waiting, they figured out it wasn't going to happen and left. Try and see it from that perspective.