Dan Drezner (UPDATE: better yet, see his post directly on the test) showed great timing, blogging about North Korea just a couple of days before the 2nd NK bomb test. This test, unlike the first one, may not have been a dud. But the question of the day is: does this test really matter? That is, does it change the strategic equation on the peninsula? Does it change our views of North Korea? What difference does it make?
Strategically, this bomb does not change much. The US and its allies (Japan and South Korea) have already been deterred from attacking North Korea--not so much because of its reputed nuclear arsenal, but due to the conventional balance. At the start of any war, North Korea would level Seoul with its artillery, causing massive damage. These guns are underground and can pop out, shoot and pop back. Over the course of much time, they could be knocked out by US air power and missiles, but the damage would be done. So, no bombing or invasion of North Korea, bomb or no bomb. Indeed, I compare North Korea to Iraq to ask the question of why the US attacked one and not the other--and low hanging fruit (Iraq) is one of the likely answers.
Politically, it is more complicated. The bomb test is likely to reinforce existing beliefs about the intractability of the problem, the difficulties of bargaining with North Korea, and the like. Drezner was quite right to criticize the Kreminology of North Korea--essentially reading tea leaves to figure out which leaders are rising and falling and what their positions are. This test does indicate that North Korea is not moving in a more cooperative direction, but the recent missile tests sent the same signal. It is clearly a signal to the Obama Administration that a new US government is not going get the benefit of the doubt or any concessions in the near term. Indeed, this test demonstrates that North Korea does not care too much about American domestic politics, but heightens the world's interest in NK's.
This test does make a bit clearer the limits of Chinese power. China has much invested in keeping its image as the key power in the region and as the powerbroker in North Korea's relations with everyone else. And this test, like earlier NK actions, indicates that China has very little leverage.
Where does this leave us? Deterred. With tainted concessions. Limited options at best. The good news is that North Korea seems far more interested in preventing interference in its own society than in interfering elsewhere. Which makes the North Korean bomb program perhaps a bit less dangerous and upsetting to the status quo than Iran's. Of course, that is cold comfort--it is like saying that I'd rather encounter a brown bear than a polar bear.
Update: see this for one example of speculation about politics in North Korea.