The Attack and Response:
If NK launches a nuclear weapon, what follows will depend to some extent on who and what they launched it at. It is not believed that NK has the ability to launch a mid-long range nuclear attack. In other words, they can’t hit the US from Asia. Their only viable/realistic target option for a nuclear strike is South Korea.
A nuclear response depends on a state’s second strike capability – their ability to continue a nuclear war after the first salvo. If NK launches a nuke, the probability that their missile facilities will survive long enough to ever launch another one is extremely low. NK knows this, which means two things:
They know they’ll only get one shot. If they are dead set on causing an international nuclear incident, they’ll launch it at Seoul and kill 13 million people off the bat.
They know that a retaliatory nuclear response directed at them is unlikely.
Honestly, it doesn’t make a lot of sense from a strategic standpoint to nuke NK into nothingness, and China / Japan will never stand by and let that happen, to say nothing of South Korea. The ecological consequences make this too costly.
In the event that a US & SK –led coalition take military action in NK, China is going to get extremely antsy. It would require a nuclear attack, or something not far short of one, to get China to begrudgingly allow US military action there. The politics of the situation there will “ensure” a “short” war.
In other words, the campaign will end with the essential destruction of NK and the unconditional surrender of their government. An attempt by the US to occupy NK would be disastrous, but most likely it would be politically unnecessary. In this instance, the US is fighting a defensive war against a lunatic nuclear antagonist. The West will have a grace period of letting the military go in and kill like they’re supposed to before people get upset that we aren’t fixing our enemies houses and schools up nicely after we reduce them to craters. Besides, NK could use the renovations.
South Korea is Screwed:
Regardless of whether or not NK led off with or ever commits a nuclear strike, the war will transition from that point to a conventional war. Bootyuming Seoul is spared a nuclear holocaust, North Korea has 50 years’ worth of artillery aimed at Seoul and SK targets. It doesn’t really matter that they’re cold war technology; they’ll kill a lot of people.
NK stands little to no chance of resisting the US military; we’ll dominate. Whether or not we can dominate without them managing to encroach into South Korea and making the border areas a terrible place to live is another question. Probably not.
North Korea has been insane about its borders, because nobody wants to live in North Korea. This means that they’ve left themselves few corridors in which to advance South, one of which is a major highway. All of these have been fortified and mined, and any bridges/overpasses are rigged to blow in the event NK tanks come rolling toward them. My guess is that NK would likely have to burrow their infantry in with tunnels under the DMZ. Either way, most of the costs vis-à-vis destroyed infrastructure (especially modern infrastructure) will be incurred by SK.
Pyongyang is a fortress city and is nigh-invulnerable to drone and air strikes, but the rest of NK is not and we can burn them out from as far away as Guam (but more likely from a fleet of submarines all around the Korean peninsula.)
SK will be burdened with most of the post-war costs.
It’s worth mentioning that NK has a standing army of 1,000,000 people. This seems like an intimidating number, and it should be. However, it’s worth mentioning a couple things:
NK is a shietshow that can barely keep the lights on. Clothing a million man army with sweatshop/slave labor and substandard materials is enough of a challenge to NK that they can barely feed anyone. Once a war starts, and they start losing supplies, food, equipment, and personnel – that’s it. They aren’t getting anymore, and they don’t have the infrastructure to produce it, especially not during wartime.
NK has to buy it’s Cold-war equipment from others. They aren’t going to be able to afford that once the war starts, and they aren’t going to be able to shift that production capability into their concentration camps.
This isn’t from experience, but from what I’m told about North Korea: North Koreans either realize what a pathetically outrageous excuse for a government they have, and wisely keep their damn mouths shut about it, orthey don’t realize anything about anything because they’ve never seen or heard of anything except the nonsense that NK spews 24/7. The folks who believe NK discovered a unicorn, but who have never heard of television.
It would definitely be foolish to underestimate ones’ enemies, but it’s never foolish to try an understand their motivations. Compare NK to Al Qaeda; AQ will “never” be defeated because they will always resist the West ideologically, no matter how many of their leaders we kill, and in fact more so because of how many of their leaders we kill. NK, on the other hand: I just don’t see these people fighting an incredibly drawn-out and sustained conflict. Like that pudgy fuk Kim Jong Un is going to rally anyone? Liberate two death camps and we’ll see how long that lasts.
NK has no realistic expectation that they will be able to win a nuclear, or sustained conventional war. Thus, their tactic is likely to make any victory over NK a pyrrhic one, where it is so costly to the US and SK that we are unwilling to see it through to the end.
This points to a likelihood of conventional warfare tactics, relying on artillery and fortified gun and AA emplacements hidden in a country that’s all mountain and forest to drain US/SK resources and raise casualties.
They don’t have to beat us, they just have to not let us completely destroy them before Big Brother China steps in and wants us to stop. China will have no patience for a decade of sustained conflict on its’ border involving anyone, let alone its’ rival superpower.