The question is did Claude really enable them - or just make it more convenient?

While it’s not your every-day coding exercise - I boldly suggest it’s probably not that hard to code a ballistic missile guidance system without AI.

The hardware would be the harder part!

Doubtless it gets advanced at the top end, but the fundamental physics involved isn't national-secret level, so something that "works well enough, most of the time” would be within reach of most organised groups.