I've been thinking about nukes lately (way too much, in fact). And, IMO, the only people who want nuclear weapons are national leaders. If the US invaded North Korea tomorrow, then NK has three options:

1) Launch nukes at the US. The minute those missiles leave their silos, the US will launch theirs. Even assuming the best case of no other nations joining in, most residents of NK and many residents of the US are either dead or going to die soon. The leaders of NK are probably dead.

2) Fight a conventional war. NK will probably hold out fairly well using drones. If they learned from Iran's diffuse decision-making in the military, they'll do even better. They might hold off the US long enough for peace talks. Leadership has a chance to survive, more so if they flee to China or Russia.

3) Capitulate immediately. Leadership flees to China or Russia, and the US probably lets them. The citizens aren't massacred or conscripted into a massacre, and they go on living their lives.

For NK citizens, the order from best to worst is scenario 3, 2, then 1 (if NK had good human rights, the order would be 2, 3, then 1). For pragmatic leadership, it's 2, 3, then 1. For crazy leadership, it's 1, 2, then 3. In the long run, every country will have a crazy ruler.

And that applies to any two countries. If Russia invaded the US tomorrow, I'd prefer we put up a good fight with conventional weapons, and then surrender if that fails. No nukes. I would rather live a mean life under Putin than watch my family suffer radiation poisoning. At least there's a chance of improvement and rebellion with the former.

Thinking more about it, is there any good circumstantial evidence that nukes have deterred war? Conventional war between any major powers would be devastating to everyone's economy. When the USSR was falling apart, they knew it was because of their own system and choices. Was would have just made things worse. The US goes to war with weaker nations and still leaves before winning, because we're a democracy and wars are very unpopular.