Wars are very rarely (read as never) fought as total wars to the death. Nobody can predict what exactly would happen if the conflict turns violent. The range of outcomes is huge. The regime may not be able to sustain itself if a war breaks out. There could be mass surrender/defections. Certainly it's hard to see how NK can sustain a war for any length of time given the state of its economy and the resources it has. The worst case scenario is indeed very ugly but IMO not very likely. As crazy as the regime appears to be, self preservation must be one of its objectives.

Are you trying to argue that there is a moral difference between action and inaction, or just a political difference? It's certainly something that historic philosophers have spent a lot of time discussing, but that doesn't mean their moral confusion needs to be taken seriously.

Any use of power against other people is necessarily both a moral and a political question. I wouldn't take someone seriously who ~hasn't~ thought hard about the moral question involved.