North Korea announced that it had tested a second nuclear device yesterday, a move which immediately earned the condemnation of the international community. Initial reports indicated that the explosion was in the 15-20 kiloton range (roughly the size of the Hiroshima bomb) but those reports appear to have been mistaken; the bomb was probably fewer than 10 kilotons, and perhaps less than four. This suggests either that the test was not completely successful, or that the North Koreans are trying to skip several levels of nuclear design by creating minaturized, low-yield nuclear devices that might fit on the end of a missile. I'd bet pretty heavily on the former possibility, as it took the United States and other nuclear powers a very long time to figure out the dynamics of small nuclear weapons. Response options are limited. North Korea is already so isolated that additional sanctions (and additional condemnation) has only marginal effect. The success of any action against North Korea depends to great extent on the attitude of Russia and China. Beijing, which would be forced to bear many of the costs of a North Korean collapse (and which probably has much better information than we about the prospects for collapse) has been reluctant to put much pressure on the regime, although it has signaled its displeasure with Pyongyang's brinksmanship. North Korea is believed to have enough plutonium for five to eight bombs. Assuming that this device was plutonium, that leaves another 3-6 potential weapons. Given that the first test failed and that this test may not have been a complete success, the actual military import of the weapons is so far minimal. North Korea's devices don't appear to work properly, likely can't be weaponized, and North Korea doesn't have delivery platforms (missiles) that can be relied upon. North Korea may have a backup uranium program, which is relevant because uranium devices are so simple that they don't need to be tested. Still, these failed tests have the very real cost for North Korea of substantially reducing its nuclear capability. --Robert Farley
