I feel like I've missed some context here. Currently we do not have a city on Mars, nor have we developed nuclear missiles which can deliver a payload to Mars.

I feel like I've missed some context here. Currently we do not have a city on Mars, nor have we developed nuclear missiles which can deliver a payload to Mars. I'm sure that such a thing is within our grasp, but a military still has to be incentivized to build an interplanetary nuclear weapon stead of spending that defense budget elsewhere. If the martian cities cannot strike from Mars, then there is little incentive to building the capability to destroy them. Anyhow, what are we talking about here? Why did the topic of Mars and avoiding nuclear armageddon come up?