Siegfried Hecker has the rare distinction of being an American who has visited both North Korean and Russian nuclear facilities. An expert on plutonium science and a professor at Stanford University’s Center for International Security and Cooperation, Hecker is also a former director of the Los Alamos National Laboratory. Here he answers questions on Pyongyang’s nuclear capabilities, its most recent missile test, and what influence the new president of South Korea might have on the regional balance of power. He explains how North Korea developed its arsenal despite global opposition, and says there is no conceivable way the United States can destroy all North Korean nuclear weapons with military might.
BAS: Is North Korea currently capable of delivering any nuclear weapons any distance? How do you know?
SH: We know they have nuclear weapons that work because they have tested five nuclear devices over a period of 10 years. That test experience most likely enables them to miniaturize nuclear warheads to make them small and light enough to mount on missiles. They have also demonstrated over many years that they can launch relatively short-range missiles reliably. We have to assume they can mate the warheads and the missiles so as to reach targets anywhere in South Korea and Japan.
BAS: What does Pyongyang’s most recent missile test, which took place on Sunday, tell us about their capabilities and intentions?
SH: The missile experts are still analyzing the test as North Korea releases details and photos. However, they already agree that this missile outperformed any previous North Korean missile launch. It is reported to have traveled nearly 800 kilometers (497 miles) for 30 minutes (splashing down in the Sea of Japan south of the Russian border) and reached an altitude in excess of 2000 km (1243 miles). Since it was launched in a lofted trajectory, it may be able to travel at least 4,000 km (2486 miles) if launched on a standard trajectory.
This would make it a real intermediate-range ballistic missile that puts Guam within range. But the more important objective of this test was to move North Korea closer to having an intercontinental ballistic missile (ICBM).
BAS: What sequence of events might lead Kim Jong-un to launch a nuclear attack on one of its neighbors like South Korea or Japan?
SH: I cannot imagine any circumstance that would lead Kim Jong-un to launch an unprovoked nuclear attack on anyone. However, we know so little about him and even less about the military that controls the country’s strategic rocket forces that we can’t rule out a miscalculation or a desperate response to a crisis. It is conceivable that they believe a small nuclear weapon could be used to de-escalate or terminate a conventional confrontation on their terms.
BAS: How big is the largest nuclear bomb tested by North Korea, and can you give a sense of the level of damage such a bomb would cause?
SH: The highest yield of the North Korean tests to date is in the range of 15 to 25 kilotons—an explosive power similar to the bombs that destroyed Hiroshima and Nagasaki, causing roughly 200,000 immediate fatalities and lingering radiological health effects for many survivors. If such a weapon were to be exploded over Seoul, it is possible that several hundred thousand people or more would perish.
BAS: If Pyongyang were to attack South Korea or Japan, what would be the immediate and longer-term effects?
SH: The immediate effects would be horrific, the longer-term effects catastrophic. If several bombs exploded over South Korean or Japanese cities, there could be a million or more casualties. Beyond that, the cities would face massive evacuations and long-term building and grounds decontamination efforts. Dangerous radioactive clouds would drift over South Korea, Japan, China, or Russia, depending on the wind flow. An international order would be destroyed.
BAS: How close is North Korea to being able to attack somewhere as far distant as the United States with a nuclear weapon? What technical leaps does it need to make to achieve that capability?
SH: I believe that North Korea does not yet have the capability to reach the US mainland with a nuclear-tipped missile. It has a very sparse and not very successful long-range rocket test history, although the missile test on Sunday brings it somewhat closer. Its solid-fueled rockets, which are of greatest concern because they can be launched quickly and from hidden locations, have failed regularly. It will need to miniaturize warheads to a much greater extent than it is currently likely capable of doing, and the warheads will have to survive the stresses at launch and the high temperatures and stresses during re-entry. At the current pace, North Korea may be able to make the technological progress required for a nuclear-tipped ICBM in five or so years.
One corollary question that one must ask, however, is why would North Korea want to strike the US mainland? It is quite clear that it wants to threaten Washington with such a capability, but to launch would be suicidal, and I don’t believe the regime is suicidal.
BAS: Besides being able to threaten the United States and its allies, what else could the Kim regime be trying to accomplish with its nuclear weapons?
SH: We need to look closely at how the North’s growing nuclear arsenal may change its domestic policies and foreign relations. Domestically, the nuclear arsenal may help justify the regime’s continued call for sacrifice by its citizens. But it may also provide a more solid foundation for the state’s security, allowing it to devote more resources to economic growth. Foreign visitors have reported that living conditions in Pyongyang have improved markedly in the past few years despite international sanctions. Kim Jong-un has officially promoted the dual policy of military and economic growth.
Looking abroad, the regime’s nuclear arsenal could make it more aggressive in dealings with South Korea and the rest of the region. We have not seen a return to the North’s especially aggressive behavior of the late 1960s. Nevertheless, being one of fewer than 10 states in the world with nuclear weapons may change Pyongyang’s foreign policy toward its neighbors. And we don’t know how possessing a nuclear arsenal will affect the regime’s behavior in a crisis.
BAS: Is it plausible that a US pre-emptive strike could destroy all North Korean nuclear weapons, fissile material, and nuclear production facilities? Why or why not?
SH: There is no conceivable way the United States could destroy all North Korean nuclear weapons. It is not possible to know where they all are. Even if a few could be located, it would be difficult to destroy them without causing them to detonate and create a mushroom cloud over the Korean peninsula.
It is even less likely that the United States could locate and demolish all of the North’s nuclear materials. Missile launch sites could be destroyed, nuclear test tunnels could be bombed, production sites could be destroyed, and North Korean missiles could possibly be intercepted after launch. But North Korea is developing road-mobile and submarine-launched missiles, which cannot be located reliably. New test tunnels can be dug. And while we know North Korea has covert production facilities, we don’t know where they are. The US military may not be able to intercept missiles after launch. The bottom line is, military strikes could be used to set back the North Korean nuclear program but not to eliminate it.
Moreover, I believe the US and South Korean governments consider the consequences of any military intervention unacceptably high—in spite of the proclamation that “all options are on the table.” I believe the military option will only really be on the table if North Korea initiates military actions.
BAS: There is talk that North Korea is about to conduct a sixth nuclear test. What do you make of these reports? Do you have any insight into what to expect?
SH: North Korea has ample technical reason to test again as it moves toward developing a credible nuclear-tipped ICBM. The test site appears to be ready. I believe the only thing that inhibits them from testing is the political fallout they would face—particularly from China and the new South Korean administration.
BAS: You recently estimated that North Korea has 20 to 25 nuclear weapons. How do we know?
SH: My estimate that it has sufficient plutonium and highly enriched uranium for 20 to 25 nuclear weapons is highly uncertain because we know so little about its uranium enrichment capacity. All estimates are to a large extent based on the observations my Stanford colleagues and I made during my last visit to Yongbyon in November 2010. To my knowledge, no outsiders have been in their nuclear complex since. So the only direct evidence we have is from that 30-minute tour and discussions with their experts at the centrifuge facility. The rest of the estimate is based on indirect evidence—that is, satellite imagery, and what North Korea chooses to publicize, combined with modeling of their capabilities and acquisitions.
BAS: North Korea carried out its first nuclear test in 2006. How was it able to go from that widely condemned first test to today’s arsenal despite global opposition?
SH: How they developed a threatening nuclear arsenal despite global opposition is a sad reflection on unwise US policies and the international community’s approach to preventing nuclear proliferation. Controlling the supply side of proliferation has been the predominant international mechanism for halting nuclear weapons development, but it failed terribly in the North Korean case. The international export system is leaky enough that a determined government can develop indigenous bomb-building capabilities over time. In North Korea, this process was exacerbated by the fact that once they built the Bomb, sanctions and isolation allowed them to build a whole arsenal instead of forcing them to give it up.
Insufficient attention has been paid to the demand side—that is, to why states want nuclear weapons and what can be done to influence the decision to acquire them. In the North Korean case, the Clinton administration greatly slowed North Korea’s drive to the Bomb with diplomacy. The Bush administration rejected diplomacy, but was unprepared for the consequences. It stood by while North Korea built a nuclear weapon. Subsequent attempts at diplomacy amounted to too little, too late. (This should serve as a lesson on the Iran nuclear agreement: if you kill a deal, you better be prepared for the consequences). The Obama administration was greeted with a North Korean nuclear test in 2009 and was never able or willing to pursue diplomacy effectively. It relied on two tactics, imposing sanctions and pressuring China, while North Korea continued to build its arsenal. Washington and Beijing never got on the same page on how to deal with Pyongyang.
BAS: South Korea just elected a new president who takes a more conciliatory approach to North Korea than his predecessor. How might this affect the North’s nuclear activities?
SH: In the end, the Korean peninsula nuclear crisis has to be resolved to the satisfaction of the Korean people. South Korean President Moon Jae-in favors diplomatic engagement with North Korea. I believe that at this point, it is imperative for Seoul and Washington to craft a unified strategy on North Korea and speak with one voice. That voice should reflect the new South Korean president’s views on finding a diplomatic resolution. I hope that the Trump administration will support President Moon, and that Pyongyang won’t pre-empt diplomacy with a nuclear or long-range missile test.
BAS: If you were advising president Trump, what would you tell him to do in the next month regarding North Korea? In the next six months? The next year?
SH: In the next few weeks, after consultation with President Moon, President Trump should send an envoy to Pyongyang to tackle the most immediate danger—that is, to avoid a nuclear detonation on the Korean peninsula. There is a danger that overconfidence or miscalculation by Kim Jong-un, or an unpredictable reaction to a crisis, could result in a nuclear detonation. I also have serious concerns about a nuclear-weapon accident in North Korea, particularly if Pyongyang feels threatened and begins to deploy its nuclear arsenal. Moreover, in the case of upheaval or chaos in the North, who will control the weapons, and what will become of them?
The next six months should be followed up with additional bilateral US-North Korea dialogue, with Washington separately keeping Seoul and Beijing informed. Washington should stress the seriousness of the situation, but also listen to the North’s concerns.
These dialogues may then lay the foundation within the next year for a resumption of multilateral negotiations to halt, roll back, and eventually eliminate North Korea’s nuclear weapons. Talks could also lay the groundwork for normalizing relations between the North and its neighbors and the United States.