&gt; what prevents a conventional war from breaking out on the scale of WWII or even larger?<p>The same MAD principle? The knowledge that after 6 years, everybody will be exhausted by fighting, and what for exactly? Hitler wasn&#x27;t rational, and maybe he would use nuclear weapons. Actors in the WWI thought it would last couple months, again, weren&#x27;t exactly rational about what they are getting into.<p>It&#x27;s not nuclear weapons what creates peace. It&#x27;s the rational ability of humans to (eventually) see the hopelessness of destruction, that creates peace.<p>Whether the destruction comes from nuclear or normal weapons is irrelevant, however conventional weapons at least give us chance to have that rationalization later. In other words, stronger weapons require more responsible humans, not cause them to be more responsible.<p>The MAD doctrine is just a false rationalization of irrational fear. It is not a rational principle, it is principle adopted so that humans can feel better having nuclear weapons, although having them objectively makes the world a more dangerous place. If people indeed followed MAD doctrine as rigorously as MAD doctrine itself assumes, WWI and WWII would never have happened either.