Skirmish and proxy wars can be carried out without turning to the nuclear option. For instance Vietnam was in part a proxy war between the US and China -- both

Skirmish and proxy wars can be carried out without turning to the nuclear option. For instance Vietnam was in part a proxy war between the US and China -- both nuclear powers at the time. Even outright war might not result in the nuclear option if it looks unlikely to threaten a nation's sovereignty. There is asymmetric warfare. Imagine a scenario where a large unit of e.g. terrorists attack a city. Imagine what just 100 armed and armor wearing individuals could do. This would likely result in a military response and the skill/capability of the military is largely going to determine the outcome and 'efficiency' there. Finally there is also the issue that nuclear deterrence may not always be a thing. Anti-missile technology is constantly improving and we could develop even more efficient means of developing any sort of concentrated nuclear threat. If and when we reach this time, the world's geopolitical equilibrium would radically shift overnight and trying to play catch-up from that point would be unlikely to be effective.