First off, does North Korea possess a functioning nuclear weapon?
I know that any answer can only be speculative, but there are usually some strong indicators that a country has nuclear bombs. The strongest and most reliable one being an actual test of such a device. Nowhere has there been any mention of North Korea ever performing such a test. For many decades there have been in place the extremely sensitive seismometers needed to pick up even a low yield nuclear test by North Korea. It is extremely unlikely that North Korea was able to develop an atomic weapon before the advent of this sensing array.
Another way of testing such a device without actually detonating it is through digital simulation. There are many design verification methods that use computers to validate the functionality of a nuclear weapon’s engineering and construction. The odds of North Korea owning such an advanced data processing facility are near zero. In addition, they would also need a large team of highly specialized systems analysts and programmers to reliably run such a computer. To my knowledge, no one sells off-the-shelf thermonuclear device design functionality verification software packages. These sort of applications are among the most closely guarded state secrets of any nation who has one. North Korea would be hard pressed to generate the code for such a package on their own.
A final and equally remote possibility is that North Korea acquired a thermonuclear device from another country with a proven track record of developing reliable weapons. Once again, this is highly unlikely. Given North Korea’s long history of deranged leadership, few other nations would deliver an atomic weapon into their hands. The only potential candidates would be China, the now defunct Soviet Union or (remotely possible) South Africa. It is doubtful that communist China would ever allow a nuclear bomb out of their grasp. Given the ability to accurately trace byproduct isotopes to a certain reactor and extraction facility, no country would want to be held responsible for releasing such a potent weapon into the hands of so unstable a government.
Should the Soviet Union have sold one to North Korea, it could be quite possible that such a warhead would no longer be functional. The compression and lensing explosives have a limited shelf life that would have expired by now. All of this leaves us where we started. Does North Korea really possess the skilled scientific staff and specialized facilities to have manufactured one of these weapons? While North Korea is in the habit of diverting vast portions of their economy towards military projects, even at the cost of starving their own population, the cost of developing atomic weapons remains quite high. Inert gas environment machine shops, extraction and purification equipment, shielded handling facilities plus remote sensing and manipulation all carry huge price tags. There are also a host of highly specialized materials and manufacturing techniques that do not come cheaply either.
All said, owning such a weapon is pretty much decorative unless there is absolutely certainty that your design and assembly procedures are adequate. In the absence of reliable computer modeling, only a live test provides conclusive proof of principle. It is almost doubtless that North Koreas has never performed such a test. Where does this leave us?
North Korea may or may not be in possession of one or two warheads that may or may not work. Hardly the stuff of a superpower confrontation. Worrisome, yes. Worthy of walking on eggshells about? Maybe not.
Another big question concerns North Korea’s supposedly gigantic array of field pieces sighted upon Seoul. While South Korea’s capitol is the exact opposite of a moving target, there remain other considerations. A quick check reveals that modern American munitions may be required to have a twenty year shelf life. It is safe to assume that North Korea’s artillery munitions are less modern and have a shorter shelf life. In a country that is perennially on the brink of starvation, how likely is it that these millions of shells have been routinely replaced or reloaded? The cost of doing so on a regular basis would be quite extreme. North Korea seems to be rather short on the cash needed to do this very often.
For some time now in the United States, there has been in place a doctrine whereby any use of chemical or biological agents will be met with nuclear retaliation. It is difficult to imagine that North Korea’s military and government are unaware of such ramifications. That they would willingly risk total annihilation over the firing of much less effective chemical or biological weapons is highly illogical. If their first volley contains atomic weapons, they are equally as dead. In spite of whatever bravado and bluster they exhibit, the fact remains that North Korea is faced with an all or nothing situation. This balance of power could shift should they gain possession of and successfully test additional nuclear weapons. That this makes some sort of military action imperative is not entirely germane to the topic under discussion. However, the questions remain:
Does North Korea represent a credible nuclear threat in their current status?
Does North Korea stand to gain substantially by using chemical or biological weapons?
Does North Korea possess sufficiently functional conventional military forces to prevail?
I find the answer to all three questions resoundingly negative.