Again, the story pre-dates 2400.0 and the story is based off of the Conquest mod, not yet released.
Physics of that mod work differntly and given the fact that they have not yet discovered, or re-discovered space travel, neucler weapons are all they have at the moment. Crude and effective.
CSM my have neucler war heads, but they could be low yeild or even neucler waste by products like depleted urianium. Just a thought.