It will be interesting to see that who will 'liberate' North Korea and how.
Edit: that assumes that SK would be the 'liberator', but chances that it would be China are probably higher.
While they will end up killing lots of people and causing heavy economic damage the real inability to deliver on the threat that has been kept alive by those who want a stronger stance against North Korea is likely one reason they are pursuing nuclear weapons. They know they don't have a strong threat and they want one. Whether this is to truly for self protection or for aggression is for teh intelligence wonks to figure out
http://thebulletin.org/evidence-shows-iron-dome-not-working7...
Also don't forget that next after artillery fire the NK can march in couple millions of soldiers - short of nuclear strike there is no way of stopping such a mass of infantry.
Not to mention that even if N. Korea were to be "liberated", I'm not entirely sure the South would want to bear the cost of reunification. Korean reunification would make German reunification look cheap in comparison.
But for US situation with NK and SK is already good enough: no profit from invading NK, and US already profit from having military base in SK because SK pays them huge money for it.
USA gains nothing from invading NK. When any variable change and invasion will become profitable, NK will be inevitably "liberated".
A 2011 article from The Atlantic concerning Pakistan's nukes [1] offers clues as to how North Korea's arsenal might be rendered safe:
"This 'disablement campaign,' as one former senior Special Operations planner calls it, would be the most taxing, most dangerous of any special mission that JSOC could find itself tasked with—orders of magnitude more difficult and expansive than Abbottabad.
...
JSOC would take the lead, however, accompanied by civilian experts, and has been training for such an operation for years. JSOC forces are trained to breach the inner perimeters of nuclear installations, and then to find, secure, evacuate—or, if that’s not possible, to 'render safe'—any live weapons. At the Nevada National Security Site, northwest of Las Vegas, Delta Force and SEAL Team Six squadrons practice “Deep Underground Shelter” penetrations, using extremely sensitive radiological detection devices that can pick up trace amounts of nuclear material and help Special Operations locate the precise spot where the fissile material is stored. JSOC has also built mock Pashtun villages, complete with hidden mock nuclear-storage depots, at a training facility on the East Coast, so SEALs and Delta Force operatives can practice there.
At the same time American military and intelligence forces have been training in the U.S for such a disablement campaign, they have also been quietly pre-positioning the necessary equipment in the region. In the event of a coup, U.S. forces would rush into the country, crossing borders, rappelling down from helicopters, and parachuting out of airplanes, so they could begin securing known or suspected nuclear-storage sites. According to the former senior Special Operations planner, JSOC units’ first tasks might be to disable tactical nuclear weapons—because those are more easily mated, and easier to move around, than long-range missiles.
In a larger disablement campaign, the U.S. would likely mobilize the Army’s 20th Support Command, whose Nuclear Disablement Teams would accompany Special Operations detachments or Marine companies into the country. These teams are trained to engage in what the military delicately calls “sensitive site exploitation operations on nuclear sites”—meaning that they can destroy a nuclear weapon without setting it off. Generally, a mated nuclear warhead can be deactivated when its trigger mechanism is disabled—and so both the Army teams and JSOC units train extensively on the types of trigger mechanisms that Pakistani weapons are thought to use. According to some scenarios developed by American war planners, after as many weapons as possible were disabled and as much fissile material as possible was secured, U.S. troops would evacuate quickly—because the final stage of the plan involves precision missile strikes on nuclear bunkers, using special 'hard and deeply buried target' munitions."
[1] http://www.theatlantic.com/magazine/archive/2011/12/the-ally...
Anyway, I hope NK understands that any kind of unprovoked offensive nuclear action on their part will result in the rest of the world banding together to crush them. I think they do understand that. It would probably happen to any country that uses a nuke offensively, and maybe defensively too.
If the US was planning a coup, why would they bother destroying all of their nuclear weapons?
It's merely discussing one such event that could lead to this plan being used, though the risks of failure mean it's unlikely to happen without a coup. What could North Korea do to make it seem like an attack was imminent and then leave enough time for this plan to take place?
North Korea will only use nukes if they're in threat of being crushed anyway, or if they have the support of China and either Russia or the US.