I am too new to answer peoples questions, so I decided to post my own to frame the problem a different way. People assume that nuclear states hold nuclear weapons only to deter intimidation from other nations that hold them. However, it is not the only reason. In the case of a strike against a nation, which dooms the state that doesn't strike first, why would that doomed state not retaliate? Given that the conflict in the first place was about world governance, why would an attacked nation give the world over to this aggressive state by not firing back and turning that place, its capital cities and its industrial base, into a glass carpark?
Any people who were to have survived from the nation that was first doomed, would then be subjugated to the aggressor nation, probably forever.
In addition, the attacked nation may believe that all mankind is facing this aggressor in some way, and that the aggressor is a problem for mankind's future. If so they will make a decision to throw the boss out the window for everyone else. Yes a lot of people will die, but a valuable lesson will have been learned by humanity about where stupidity and arrogance gets you.
As far as the environment is concerned, they will say to themselves "it was unilaterally decided that planet earth could handle one country being annihilated by nuclear weapons, we think there's room for one more".
Finally, the attacked nation will believe that they are morally in the right - if so, why should the other go unpunished?
Tell me if I'm not thinking straight please. But if one gets attacked, the other IS GOING TO FIRE BACK. Please tell me that is crazy talk, it will be amusing....