I was wondering what reasonable realistic tech advancements it would take in order for a long nuclear war between major power to be possible. That is to say, longer than 6 years in length of regular fighting. I don't mean a nuclear sub nuking a city for the dozenth time 7 years after WWIII. I mean a real war where economies are shifted to military production, tech advancements are made, ect... Of course, you need cities for that, so, I would assume you would need very, very, very impressive AA capability, rendering not only nukes, but the entire combat part of the airforce useless as well. What else?