Nuclear is taboo, but a mass moving at high velocity in space and then impacting the Earth is just as powerful, if not more so. Seeing it launch, and knowing it is coming but unstoppable except through leveraged diplomacy is more strategic. The timeline is long, but the potential for a redistribution of geopolitical power structures is large.

I think it is likely a distant future type of problem. Refueling of a large craft in space is likely a major factor, but we are nearly at that point now. I am curious if such a technology comes before large scale space colonies or after. Does it make more sense to weaponize some low earth orbit asteroid for the mass, like covering the surface with an expanding ablative resin before redirecting it to a target.

If all major wars last for years, when (if ever) does it make sense to have a launch platform around a Jovian moon for the largest gravitational assist.

Not that I want any such thing. I am thinking about hard science fiction and the overall timeline.