I made this account to share this idea i had.
If everything about this theory is true, then the Buster Call might be Uranus, since it comes from the sky, and is way more advanced then any other technology they have access to.
I mean it destroys islands, it would make perfect sense that the marines acquired it somehow after the war. I would also speculate that it is some sort of a moon station or something that concentrates the sun into a ray, that can be pointed where ever.
What do you think, i think this makes perfect sense.