Nuclear weapons cannot be used against other nuclear powers, but - as a last resort at very small scale, very carefully, in principle, after threatening first - against standing armies of wannabe super soldiers...
(Then again that kind of world still seems very unsafe and the more people can press the button, the higher the risk that someone will. So maybe drones against wannbe biological overlords instead in the future? Not to happay about robo drones either but perhaps have to pick the smaller evil. idk im open to ideas that will make earth safer (really safer not some excuse for authoritarianism))