N Korea is playing nice now, claiming they're willing to talk about scrapping their arms program, but the whole negotiation looks like an exercise in futility. The N Korean regime's only real fear in the world is that Washington will remove them from power. They see nukes as the only deterrent from that scenario. They will never give them up -- and if they claim to, you can bet your last dime they're lying just as they were in 1995.
Dean Emay wonders whether the N Korean's military power is all it's cracked up to be. I would say emphatically no; their main purpose is simply to keep the regime in power. Even if they had ambitions of conquest, there is no conventional threat in the world that a single U.S. carrier group could not defeat -- and iirc, we curently have around 12.
This was not the situation 20 or even 15 years ago. The large number of precision-guided munitions, especially JDAMs, which have become available have changed the game immensely. We can now hit something like more targets in one week with one carrier group than the Allies hit in all of WW II. In the old days, they had to fly a hundred sorties to be sure of hitting a target; now one will usually suffice for several targets.
Of course, the problem with N Korea is that they have enough artillery already in place to obliterate most of Seoul within hours. Hours is likely all they would have, but unfortunately that's all they need to level a good chunk of S Korea's major city. That makes an offensive war against them a very politically unpalatable and therefore unlikely scenario.
Like China, N Korea will almost certainly have to collapse or reform from within rather than through use of force. It would be easy to cause that from a practical standpoint — just cut off all aid, and half of them would starve to death in 5 years, and eventually massive food riots by the army would bring the gov't down (from a political and humanitarian standpoint, that's a much dicier prospect). The regime stays in power by feeding the army first, and everyone else if there's anything left, so as long as there's aid coming in they'll survive because all the guns are in their control. Sadly, the DPRK regime is essentially using its own civilian population as a blackmail tool to get enough aid from China and the West to feed their army.