As if understanding North Korea weren’t already hard enough, Pyongyang threw the world a new twist this week when it claimed to have tested a nuclear device. If the Hermit Kingdom is telling the truth about the nuclear nature of its test, it detonated a device that was 40 times less powerful than most expected it to be. Foreign policy observers seem confounded about what this means. Most say that it reflects a technically weak North Korea, as headlines reporting “a dud” attest. A minority initially speculated that the low explosive power was intentional, reflecting a more sophisticated North Korean design.
But, while the bomb’s power isn’t unimportant, they’re largely missing the point. The bomb may have been weaker than expected, but that doesn’t change the strategic problem of a nuclear-armed North Korea or the basic significance of the nuclear test. The things that matter most are that North Korea has the bomb, and that it appears willing to defy international opinion in handling it.
Nobody yet knows why the Korean explosion was so small, so many have focused so far on answering that question. A first-generation plutonium-based nuclear bomb, like the one the United States tested in July 1945 and the one it dropped on Nagasaki a month later, is normally expected to have an explosive power of roughly twenty kilotons. But the one the Koreans tested was roughly 500 tons.
One explanation is that the explosion may have been conventional, not nuclear. Yet this is probably not the case. Coordinating the detonation of several hundred tons of conventional explosives is not a simple task. More importantly, if any country could demonstrate that the detonation was indeed conventional, it would cause North Korea profound humiliation.
Another explanation is that the test may have been a partial failure. In an implosion bomb, which most believe North Korea has developed, high explosives are used to compress plutonium. If the explosives compress the material partially, but not as much as expected, the explosive power is reduced.
A third possibility is luck. A nuclear detonation depends on a certain random element. For this reason, U.S. military analysts estimated that the Nagasaki bomb, before it was dropped, had a twelve percent chance of falling short of its 20-kiloton potential. North Korea may have been unlucky in its roll of the dice.
A final theory holds that North Korea chose to test a more sophisticated weapon whose power was lower by design. Yet North Korea apparently told China that its bomb would have a power of four kilotons—substantially larger than the actual explosion.
But, while these considerations are important from an intelligence perspective—they give us insight into the state of North Korean technology, and counsel us that North Korea might attempt another test —they don’t change the broader outcome. North Korea is unlikely to feel any less secure because it failed to meet expectations, and the United States and South Korea are unlikely to feel emboldened. Does anyone, including Pyongyang, seriously think that we will now contemplate an all out military attack simply because the North Korean test was only a partial technical success?
In fact, the messages North Korea has sent have little to do with the technical details. Pyongyang has signaled that it may not be deterred by international warnings, even if those warnings come from erstwhile friends like Beijing. Of course, the nature of those warnings matters. The basics of nuclear deterrence haven't really changed: North Korea gambled on the world’s reaction to its test, but it is unlikely to gamble that it could launch a nuclear attack without suffering severe retaliation. And China's admonitions not to test might have been taken more seriously if Beijing had chosen to spell out explicit consequences for Pyongyang. (Beijing vagueness unwittingly invited North Korea to think that it was calling China’s bluff. Whether it was actually a bluff is still uncertain—China has responded with harsh rhetoric, but its ultimate response is still uncertain.)
What’s more, with yet another nuclear milestone in its wake, Pyongyang is even less likely to give up its arsenal. This is the third red line it has crossed—it chose to develop nuclear weapons, to expand its arsenal, and to test, all against international opposition. Dealing with the last two violations (stopping North Korea from testing again and from further expanding its arsenal) will be challenging enough; rolling back the entire program is essentially impossible. In the long term, this may prompt others in the region—such as Japan and South Korea—to pursue their own nuclear programs, even as they forswear such possibilities now. Their decisions to do so won’t hinge on size of the nuke North Korea unleashed earlier this week, but on the fact that it detonated a nuke at all.
To be certain, specifics about North Korea’s weapons can’t be ignored in military planning. But Pyongyang's conventional capabilities—particularly its artillery (which is poised to rain down on Seoul)—have always presented the greatest worry, and the size of a nuclear test will not change that. Indeed, even rudimentary nuclear capabilities only add to the danger.
There’s a temptation when we think about technology to adopt a science-fair mentality, and to assume that technical issues must have substantial meaning in themselves. And it's true that we can learn a lot about the North Korean program by analyzing the technical details of its test. But the impact of the test—no matter its size—will be felt just the same in Washington, Beijing, Tokyo, and Seoul.
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