"The ultimate goal of a nuclear a weapon (as of any weapon) is to keep peace."

This certainly does not seem obvious to me. It seems eminently arguable that the ultimate goal of a weapon is to make someone else do what you want or eliminate them or punish them if they do not. Or the ultimate goal of a weapon is to kill something to eat it. Or other stuff. When the first ape-map picked up the first jaw bone with the intent of bashing in another person's head, I doubt he was thinking "I'm looking forward to keeping this peace with this."