China is my focus area, and despite that I really don't have a fix on what their strategy is. Asian diplomacy focuses a lot on back-room negotiations, because Asians highly value the notion of face, and publicly calling out countries over their activities is seen as very embarrassing. Thus, it is very surprising that over the last week or so China has been very publicly criticizing the DRPK, by name. That suggests that China has been putting a lot of back room pressure on the DPRK, that that pressure failed to result in anything, and that the Chinese are now pretty pissed off. The question isn't whether or not they want to influence the North Koreans - the question is whether they have any leverage. After all, a bomb that can hit Tokyo can also hit Beijing...

Ce n'est pas une pipe. C'est une signature.

     As opposed to a uranium bomb, the hard part of which is enriching the uranium, with a plutonium bomb (assuming access to used power-plant fuel), the hard part is actually getting a good explosive yield instead of a very-low yield explosion.  This is because plutonium has a high level of spontaneous fission, and hence the chain reaction begins much earlier, while the fissionables are still in a barely critical configuration.  To counter this, a spherical shell of precisely timed explosions are used to compress the plutonium uniformly.  A "dud" or more properly a "fizzle" explosion like this is actually the most likely result of a first attempt to test a plutonium bomb, and to even get this much of an explosion out indicates that they're fairly close to solving their technical problems and getting a "working" bomb.

     This explosion could actually have been generated by conventional explosives, or the site could have been carefully insulated and the actual explosion could have been much larger, but by far the most likely explanation is a "fizzle" nuclear weapon.  Even with a low-yield weapon like this, there would still be a significant amount of fallout.  There has been speculation for some time that the North Koreans have been reprocessing used fuel from their power reactor to use as fuel, and if, as seems likely, this is the source of the plutonium for this explosion, the number of bombs (or test bombs) which North Korea could make is probably limited to around ten.

     North Korea has for some time been attempting to blackmail the West into supplying with them with fuel oil, nominally in compensation for the electricity which they lose by not running their nuclear reactor, and actually negotiated such an agreement with the Clinton administration.  Shortly after the Bush administration took over, they claimed that North Korean enrichment activities were continuing, and suspended the fuel oil shipments, and refused direct two-party negotiations.  This provides at least one motive for the nuclear test.

     A more likely explanation, however is the degree to which, for internal political reasons, North Korea requires a serious external enemy.  Despite economic collapse so serious that North Korea is unable to come even close to feeding itself, the government remains relatively popular internally, because they have effectively used their control of information flow to place blame for their failures on South Korea and the United States.  Thus, it is much easier for North Korean leaders to maintain power in the face of international sanctions and open enmity from South Korea and the United States, than it would be if relations were friendly.

     It is unclear to what extent North Korea's leaders believe the paranoia about the intentions of South Korea and the United States which they have been teaching to their populace.

More is made than it should be of the Nakasone think tank advocating nuclearization of Japan's military and the popular abhorrance the Japanese still feel towards nuclear weapons has a strong influence in this.  Much more likely we will see increased efforts, working with the Americans, to get an effective Missile Defence Shield up and running.

Just cause you feel so good, do you have to drive me out of my head?

It's pretty clearly option (C); the DPRK leadership seems to me to be about three parts the most cynical and ruthless bastards on the face of the earth, and about two parts actually buying into their own hype.

First off, let's face a few facts:
 - The Korean War never officially ended. There's been a 50 year ceasefire, but it's still technically a war and both sides are armed to the goddamn teeth.
 - Absolutely everything they do has a propaganda value to it. It doesn't have to make sense externally, as long as it makes them look good internally. As a prime example of this, the current head of state of the North Korean government is still Kim Il-Sung, despite the fact that he fucking died in 1994.
 - North Korea has absolutely nothing going for it. They have little in the way of natural resources, lousy weather, the entire place is hills, a small population, and they're completely surrounded by regional powers. China's now more dependent on South Korea through trade and investment than they are on North Korea for geopolitical reasons. Other than this one friend-of-convenience, the North has absolutely nobody; even Chavez is smart enough to stay out of this one.
 - Despite the fact that they spend a huge proportion of their resources on the military (and they have to; the South's heavily armed, and there's 30,000 Yankees parked there too) and, to top it off, they waste a bunch of their resources for propaganda purposes, they are still here.

Which is why people rationalize the DPRK as being a bunch of Machiavellian geniuses. Because they've been dealt a shitty hand, but they're still, somehow, at the no-limit table with the big boys. They have so much opposing them, and so little going for them, and they still exist. The Great Leader, the Dear Leader and their cronies would have to be either Forrest Gump, cluelessly bumbling into great success without realizing what they're doing, or they are a bunch of Machiavellian geniuses.

I've been to North Korea; I was in the neighbourhood, and couldn't pass up the chance, so I spent a week around May Day 2005 in the country. (One group of people were playing a fun game of "Bayonet the Imperialist" in the local park.) Although you get lied to on a regular basis, you also get a feeling of what it's like under the surface, and it's absolutely unbelievable. One of our tour guides (our group had three tour guides, two of which were actually tour guides) was a 19 year old, with okay English skills. She lived in the capital, her mother was a high-ranking official. She seemed uneasy on the ride from the airport into town. We later found out this was because she had only ever met one foreigner before (there's a small handful, I believe mostly British, who are employed by the DPRK government as English tutors). The average residents -- and this woman was far better off than the average resident -- have no concept whatsoever of what life is like in the outside world beyond what they are told from their government. North Korea doesn't have the Internet, but they do have the Intranet. (Seriously, we were told this at one point.)

The country is run by a bunch of elites who live as well as they ever could in the West; all the luxuries they want. So they don't want change. The population in general sincerely believes that they are living better than in the West, so they don't want change. It's an absolutely amazing tribute to the power of propaganda, and it's one reason that Korean reunification will be a hell of a lot messier than Germany. East Germans had been watching West German TV long before the wall fell; they knew what they were missing out on.

But how long can you run this kind of propaganda scheme without having it go to your head? Kim Il-Sung is rapidly being deified in the North (they use the Juche calendar, reckoned from the date of his birth). Everything -- including this test, which falls on the ninth anniversary of Kim Jong-il's ascension as head of the Korean Workers' Party -- has an element in it glorifying the leadership. Everybody wears a pin of Kim Il-Sung at all times.

The whole place is crazy, but damn if it isn't holding together from the perspective of the people who actually run the joint.

The question being, what response can we possibly have if they do the unthinkable?  

Oh, I'd imagine the whole region would glow in the dark for a while.  While they may act someone unbalanced at times, I don't think they have a suicide wish.