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A Journey Begun Long Ago: Making Sense of the Latest North Korean Nuclear Test
By Melissa Hanham

North Korea’s nuclear test on Sept. 3 thrust the crisis of Pyongyang’s weapons program into world headlines again. It was likely a thermonuclear explosion and an order of magnitude more powerful than Pyongyang’s previous nuclear tests. State media also claim that North Korean scientists made the device compact enough to fit onto their new Hwasong-14 intercontinental ballistic missile, which can reach the US mainland. While there is much hand-wringing abroad, Asia has been dealing with the conflict for decades, and the underlying factors have not changed.


Thirty-five miles from the Demilitarized Zone, Seoul is a vibrant, robust city of nearly 10 million people — 25 million if one includes the greater metropolitan area. The capital and its surrounding areas house nearly half of South Korea’s population. Long before North Korea had nuclear weapons, it had thousands of rounds of conventional artillery pointed at Seoul. Could those devastate Seoul in the way a nuclear weapon would? No, but North Korea would not want that result if its goal was forced reunification.


Carefully targeted rockets would likely hit key military and transportation targets in Seoul and the surrounding areas in order to cause as much chaos as possible. In response, South Korea and the United States almost certainly would abruptly and completely end the Kim Jong Un regime. However, Pyongyang calculates that neither Seoul nor Washington want to risk the human and economic cost of starting such a war. Pyongyang is right.


Today, even with the additional benefit of fission or thermonuclear weapons, North Korea would lose a war with South Korea and the US. The difference is that it would be a much more devastating war. So devastating that it defies our modern understanding of war. Early seismic data from North Korea’s Punggye-ri nuclear test site suggest that the yield of the nuclear device in this latest test may be well over 150 kilotons — or more than eight times as large as the atomic bomb that the US dropped on Hiroshima in 1945. North Korea is already practicing using nuclear weapons early in a conflict to prevent invasion from South Korea and Japan.1 These exercises involve multiple missiles launched simultaneously by military units based in the field. They have even practiced launching from near a tunnel on the Reunification Highway that runs from Pyongyang to the Demilitarized Zone. The larger the explosion, the less accurate the missiles have to be.2 The more missiles launched at once, the harder it is to track them with ballistic missile defense radar.


The war and ultimate collapse of North Korea would also displace hundreds of thousands of people as they walked towards the borders with Russia, China and South Korea or floated on boats and rafts to Japan. These would be the most impoverished refugees modern Asia has ever seen. Diseases that no longer exist in South Korea and Japan still haunt North Korea’s rural areas.


Thus, today, just as decades ago, South Korea and Japan remain deterred.


While ICBMs have dominated headlines, North Korea’s conventional and shorter-range weapons actually pose a greater threat in the region. Of particular note are the new Pukguksong missiles, which are both land- and submarine-launched. These are solid-fuel missiles, making them easier to transport and fire than the liquid-fueled Scuds that North Korea already has. North Korea is also producing indigenous transportation vehicles for their missiles. Their trucks are a bit silly-looking, with long caterpillar treads instead of wheels, but they work. More important, North Korea can produce them without a lot of foreign imports. More launchers mean more missiles for outside intelligence services to track and target, increasing their survivability. It also means North Korea could produce more missiles for immediate launch. These missiles are likely nuclear-capable and, like Scud-ERs or Nodongs, could be used to deliver nuclear warheads to US military bases in Japan such as Iwakuni Air Base.


North Korea’s desire for intercontinental nuclear weapons is based primarily on its desire to drive a wedge between the US and its allies in the region. Pyongyang is calculating that the US would think twice about coming to the aid of Seoul or Tokyo if one of its own cities were at risk. It is not that simple though. The US is so firmly committed to South Korea and Japan that it has stationed nearly 65,000 active and reserve service members across the two countries.3 Japan has more US military service personnel stationed on its soil than any other country in the world. While this can cause cultural friction and frustration in communities where the US military is present, it is intended as the strongest possible expression of America’s commitment to its allies. US military families, expatriates and business people are a regular part of life in the region. An attack on South Korea and Japan is an attack on the US.


South Korean politicians have expressed doubts about this commitment and periodically called for the return of US tactical nuclear weapons to the Korean Peninsula. The George H.W. Bush administration made the decision to withdraw all nuclear weapons from South Korea in 1991. The issue of returning them, though, is largely a symbolic one. The US would not need to use locally based tactical nuclear weapons against North Korea. Bombers and submarine-delivered nuclear weapons are more than sufficient. Basing them in South Korea is logistically complicated. Nobody actually wants them in their backyard. They are also expensive, difficult to secure and make an excellent target for attack by North Korea. Nonetheless, it “sounds good” to the average person. “If North Korea has nuclear weapons, why shouldn’t we?”


South Korean military leaders understand that US strategic assets such as aircraft carriers, bombers and submarines are sufficient to respond to a nuclear attack by Pyongyang, but polling of the general public demonstrates a desire to have tactical nuclear weapons present on South Korean soil. While these are likely soft numbers that would crumble once the decision on where to base them was made, it is effective enough to have an impact on the government’s official position. On Sept. 4, South Korean Defense Minister Song Young-moo said, “The redeployment of tactical nuclear weapons is an alternative worth a full review.”4


This is a moot point. The US will never agree to returning nuclear weapons to South Korea for symbolic reasons. Instead, Seoul should take the American blood oath at face value. If North Korea used weapons of mass destruction on South Korean or Japanese territory, the US would retaliate with nuclear weapons. This is what is stated in America’s Nuclear Posture Review; it is why so many Americans are stationed in South Korea and Japan; and it is, in part, why North Korea is so eager to upset the alliance.


Another common response to North Korea’s nuclear and ICBM tests is to believe that they are in some way insufficient or impossible. Determining the nuclear and missile capabilities of the secretive state is difficult, but not impossible. Much information can be collected through open source trade data, media reports, images and remote sensing data. Nonetheless, US intelligence has continually underestimated North Korea as a backward and impoverished state.


Pyongyang has been trying to develop nuclear technology since the 1950s, when the US threatened to use nuclear weapons against it during the Korean War. The program has suffered fits and starts as North Korea initially sought outside scientific knowledge, materials and technical details. Sanctions made its illicit programs slower and more expensive, but they have not been stopped. Pyongyang has slowly produced its own weapons-grade plutonium and uranium, developed first fission, and now likely fusion, technology, and developed short, intermediate, and intercontinental ballistic missiles to carry warheads. By carefully marshaling its limited resources, North Korea has been able to do what China did in the 1960s. It is now 2017, after all, and unfortunately the technology is not getting more difficult.


North Korea has conducted six nuclear tests at its Punggye-ri nuclear test site. To the outside, these explosions present themselves as shallow earthquakes that often happen on the hour or half hour. Earthquakes typically don’t occur at precise periods on the clock and take place much deeper under the earth’s surface. Seismic stations all over the world can detect these tremors, and they report the information publicly. In addition, the Comprehensive Test Ban Treaty Organization (CTBTO) extensively records seismic, radionuclide, infrasound, and hydroacoustic data, with 288 stations worldwide currently in their International Monitoring System.5


By 2016, North Korea had conducted explosions that were approximately the size of the atomic bomb that the US dropped on Hiroshima. But this most recent test was eight times greater in terms of seismic signature, making it plausible that it was indeed the thermonuclear explosion that Pyongyang claims it was. Officially, outsiders won’t know if it was a thermonuclear weapon unless a specific ratio of isotopes in gas form escape the test tunnel and can be detected before they decay. The CTBTO and several militaries are working on this analysis today, but weather will play a significant role in whether their efforts are successful. A second, smaller seismic event was also detected at the test site. The waves from this event resemble a collapse, which is not uncommon after a particularly large nuclear test. As long as the cave-in didn’t further seal the tunnel, it makes detecting these gases more likely. Early satellite imagery collections from Planet showed that the explosion was large enough to set off landslides at the site.6 Synthetic aperture-radar remote sensing of the mountainside will demonstrate a shift in the surface of the earth.


North Korea has also presented the outside world with images of its compact warheads. In March 2016, Kim Jong Un was pictured inspecting a large silver orb. Pyongyang claimed that this nuclear device could fit on a number of their missiles. It’s true. I measured it, based on the images. What is more difficult is to determine if this object is what was exploded at Punggye-ri. Similarly, Kim inspected a large silver “peanut” purported to be a two-stage thermonuclear device capable of fitting onto the tip of a Hwasong-14 ICBM in September this year. Whether this is what was exploded hours later also remains unknown, but plausible.


In July this year, North Korea launched ICBMs not once, but twice. They followed a lofted trajectory going to a much higher altitude than distance along the ground. This has been the pattern with North Korea’s intermediate-range missile tests as well. Geographically, North Korea is surrounded by neighbors, and there is literally no good direction in which to test a long-range missile. By launching nearly straight up, they were able to simulate the path of a long-range missile.


Nonetheless, doubters pointed out that this angle did not prove that the missiles’ re-entry vehicle could survive. The re-entry vehicle protects a warhead from heat, pressure and vibration as it travels through the atmosphere. Skeptics also argue that it is not possible to know if the estimated range is accurate at that angle and weight, or if the warhead is compact enough to fit onto the missile. In a way, these are all excellent points that could cast doubt on North Korea’s capabilities. But, in reality, it doesn’t matter anymore. North Korea has done the difficult technical work. And it has been done in line with other nuclear powers despite limited resources. In the end, there is only one way to prove that North Korea can deliver a nuclear warhead at intermediate- or intercontinental ranges, and that is to actually do it.


China did just that with its CHIC-4 test in 1966. Beijing had the luxury of a large landmass and open desert to conduct that test. North Korea doesn’t. And so North Korea will likely continue to lob missiles over Japan until the rest of the world believes it is possible. One day, that missile could have a nuclear tip. We had better hope that there is no miscalculation or accident in that moment.


Melissa Hanham is Senior Research Associate at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey, California.
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    North Korea’s sixth nuclear test, in early September, generated surprise on a number of fronts — the size of the explosion; that it took place amid continuing outside overtures to engage in talks; and that Kim Jong Un was again blatantly willing to defy not only the international community but also North Korea’s only ally, China. But at some level, this test shouldn’t have been a surprise at all. Pyongyang has traveled the path to this event for a long time now, and more nuclear and missile tests can be expected. Melissa Hanham looks at North Korea’s growing capabilities and how they are aimed at sowing divisions between the US and its allies, South Korea and Japan.
    Published: September 2017 (Vol.12 No.3)
    About the author

    Melissa Hanham is Senior Research Associate at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey, California.

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