Outside of North Korea, no one knows a great deal about the nuclear device the isolated communist state detonated over the Memorial Day weekend. Seismologists have confirmed the yield of the device but beyond that the North has been typically tight-lipped.
A nuclear North Korea means many things to Asia and to the world as a whole. North Korea's test has implications for regional power dynamics, the global balance of power, international terrorism, and a host of others besides. There are doubtless a dozen questions that no one even knows to ask yet and a dozen more for which there are no good answers. Still, some ramifications of the test are fairly clear and some can be addressed with a bit of measured speculation.
What kind of nuclear weapon are we talking about here?
Seismic analysis of the Memorial Day blast puts North Korea's test between 1 and 20 kilotons in yield, meaning that it generated no more explosive force as about 20,000 tons of TNT, the rough equivalent of the bombs the United States dropped on Hiroshima and Nagasaki in 1945. Estimates differ substantially, however. Russian sources tend towards the 20 kiloton range whereas American seismologists place the yield closer to 1.5 kilotons.
North Korea's first bomb is thus almost certainly a single-stage fission device. Its small yield does not suggest the sophistication of a secondary stage. Given the North Korean's historic use of plutonium producing reactors the weapon probably contains a plutonium core making it a technological descendent of the first American atomic bomb detonated in New Mexico in 1945.
How big (physically) is the North Korean bomb?
This is the million-dollar question. When the United States developed its first nuclear weapons the devices were large and crude. The smaller of America's first atomic bombs weighed more than four tons and was ten feet in length. By comparison, a modern American W88 warhead (yield 100 kilotons) weighs about 800 pounds, less than a half-ton.
Size is important because a smaller weapon is easier to deliver to the target but a smaller bomb is a more failure prone bomb. Early American atomic weapons relied upon very simple nuclear cores whereas later designs incorporate boosted and (later on) multi-stage nuclear reactions to maximize yield while minimizing space and weight. The razor thin margins of error involved in these late-generation designs make their construction more technically challenging, however, whereas the major difficulty in building a more primitive (but heavier and larger) device is the acquisition of sufficient fissile material.
Indeed the physics behind the sort of nuclear weapons the United States developed in the 1940s are so well understood that there is very little need for a test of such a weapon. Only when the weapons get small and sophisticated is testing really necessary to know if detonation will actually occur. To that end, it is likely that a North Korean bomb is appreciably smaller than America's WWII era weapons.
North Korea had an unsuccessful nuclear test in October of 2006. The explosion measured below the 1 kiloton range, very small for a successful nuclear test, though radioactive isotopes were detected suggesting that fission had occurred albeit on a small scale. All of this is consistent with a second generation warhead design, perhaps incorporating fission boosting techniques to allow for reduced fissile mass. In other words, a small and sophisticated warhead, at least by comparison to the weapons that ended World War II.
Bottom line: North Korea can probably deliver this weapon to targets in the region by aircraft in the best case and by missile in the worst case.
How does this change North Korea's position?
As has frequently been the case, attempting to explain the actions of North Korea defies logic. The communist government there has a long history of attempting to attract Western attention by engaging in saber rattling. That said, a successful nuclear test is a significantly louder rattle than one typically sees from the North.
Assuming rationality on the part of the North Korean state, however, a certain number of inescapable truths become clear.
First, this is a destabilizing development. Regardless of the significant weapons of mass destruction that North Korea has possessed for decades, a nuclear weapon is a prized possession for any militarized state. So long as the North has nuclear weapons in small quantity it faces a "use it or lose it" scenario. An outbreak of hostilities will cause the North Korean government to preempt an expected attack against its nuclear weapons with a nuclear attack. Even a significant escalation of tensions may lead North Korea to consider an attack on its nuclear capabilities imminent. In such a situation it is paradoxically rational for the North Korean government to strike first with nuclear weapons.
Second, a nuclear test dramatically improves the bargaining position of North Korea in any negotiations yet to come. An existing nuclear weapon effectively invalidates military options in confronting the North (though some of North Korea's chemical and biological weapons could be said to accomplish much the same thing).
Third and perhaps most concerning, North Korea is a cash strapped nation with a starving population and an ineffectual economy. With little in the way of natural resources and no meaningful flow of foreign capital, North Korea may look at its newly minted nuclear capability as a financial asset. Indeed a nuclear North Korea is actually more likely to sell such weapons on the open market than a nuclear Iran despite the latter's far more obvious ties to militant extremist movements as North Korea has a great deal more to gain from such a sale.
What should the Obama Administration do?
There is not a great deal the Obama Administration can do. If the 2006 test was any indication, North Korea had nearly all of the kinks worked out of its atomic bomb project three years ago. With so much invested in the project it would take something of enormous benefit to convince the North to give up its bomb program now, particularly after a successful test.
Likewise, any serious increase in pressure or tensions is likely off the table as well. Ultimately all of these hinge upon the willingness of the United States to use military force in the region and the North will likely consider that threat a paper tiger now that it can menace its enemies with a nuclear strike.
In truth, Obama's best course of action is to do nothing. North Korea is more dangerous provoked than left to its own devices. As a newly minted nuclear power, North Korea will logically seek to bolster its own security by building additional weapons which, in turn, will serve to stabilize the power dynamics in the region. The threat of American, Russian, and Chinese nuclear responses to a North Korean launch will serve to counterbalance the North's more bellicose intentions and as the North finds itself better able to deter its enemies its foreign policy will likely become – somewhat paradoxically – less aggressive.
Moving forward from this point, Obama must remember one cardinal rule of atomic diplomacy: a non-nuclear state is preferable to a nuclear one, but a newly nuclear state is more dangerous than an established nuclear power. North Korea's test marks a most dangerous juncture for East Asia. With time, however, and a good bit of luck, today's problems will take care of themselves.