North Korea threatened nuclear war over US/South Korea wargames off the Korean peninsula. A few readers asked if this was at all legitimate.
The threats are vacuous--North Korea doesn't have any serious deployment capability. Their nuclear testing in the past has been technically successful, but not particularly impressive.
Frankly, the most damage they can currently do is rolling out a bunch of artillery and shelling Seoul into the ground. It would take a few hours at most.
This new brinksmanship is two things:
1) A litmus test to see if the US/South Korea will play more cautiously than North Korea. Turns out the answer is no, which is probably a good thing (or the precedent will be set that the US/ South Korea will retreat at threats).
2) Pump up domestic support for the nuclear program as North Koreans starve.
More interesting is the fact that Beijing's protests to wargames in the Yellow Sea caused the US & South Korea to move to the eastern shores of the peninsula. China is being particularly tough-nosed about the South Korean response to the sinking of the Cheonan, and I'm not yet sure why (unless, again, it is a part of propping up the Kim regime to keep stability strong).
Ultimately, North Korean brinksmanship will push the US and South Korea closer together. Any threats to North Korea's stability will push China and North Korea closer together. It may be the biggest foreign policy area over which China and the US will spar (barring, perhaps, American trade protectionism) now that Taiwan's Ma has taken the middle road approach to China.