North Korea was never supposed to get the bomb. For decades, the United States and international community have worked hard to prevent the spread of nuclear weapons; we’ve put in place a series of increasingly strong policies built on what we know, or what we think we know, about how countries manage to construct their own bombs. Yet North Korea successfully defied these efforts, raising a question that has long been debated by experts: Just what does it take for a country to become a nuclear power, and how can we stop it from happening? In the past year alone, North Korea has conducted a nuclear test of considerable yield and a flurry of medium and long-range missile tests. Intelligence reports suggest that North Korea is moving at a rapid clip to develop a whole suite of missiles on land and sea, may already have an inventory of sixty nuclear warheads based on a blend of fissile materials, can fit a compact warhead atop a missile, and shows no signs of slowing down despite repeated threats. There’s little dispute as to why North Korean leaders wanted nuclear weapons—to deter an attack and assure regime survival. But could it really happen? Many experts thought not. If you look at the academic theories about how nations nuclearize, few of them gave North Korea much of a chance. A program that was once derided as a “joke” is anything but funny anymore. In addition to raising a host of strategic problems for the United States, Kim Jong Un has demolished our assumptions about how nuclear weapons spread, and raises a first-order question of significant global importance: How did a nation President Nixon once derided as a “fourth rate” “pipsqueak” acquire nuclear weapons against the will of the world? How did Pyongyang manage to defy the experts? The question is more than an academic exercise. Scholarly theories about nuclear proliferation give us important insights into why and how states acquire nuclear weapons, and help policymakers build the tools to stop states from doing so. So if our theories are wrong or incomplete, then our policy prescriptions are likely to be off base as well. To put it simply: understanding why North Korea managed to acquire nuclear weapons is necessary to help ensure other countries can’t follow the same playbook. To appreciate why North Korea’s achievement was so surprising, we need to understand what experts believed—and how the Kim regime proved them wrong. A handful of big theories have driven the expert debate on nonproliferation in recent years. 1. An impoverished state can’t build a bomb. North Korea is a famine ridden, backward state—it has trouble feeding its own people, lacks access to Western technology, and its sole car factory hasn’t made a car in half a decade. One strand of nonproliferation theory focuses on technical and industrial capacity, arguing that acquiring nuclear weapons tends to require either an advanced economy, or substantial technological help from an existing nuclear power. Yet North Korea needed neither. It succeeded despite being one of the poorer countries in the world and managed to indigenously build the facilities needed to produce plutonium for weapons. While it did get some outside help – we know, for instance, that the Pakistan-based AQ Khan network assisted its uranium enrichment technology in the 1990s.—Pyongyang already had the capability to produce fissile material for weapons. And although there is a debate about the provenance of its missile components and design assistance over the years, which likely came from a variety of countries ranging from the Soviet Union (and its successors) to China to Iran and Pakistan, experts now believe that North Korea is now able to indigenously produce its nuclear weapons and many of its missiles, and has shown an impressive ability to innovate by necessity. 2. Dictators can’t manage complex projects. North Korea is run by a tinpot dictator who is a notorious playboy and once had his own uncle brutally killed. Another strand of nuclear proliferation research argues that dictatorships of North Korea’s variety are singularly incapable of managing complex projects like nuclear weapons programs. They require collaboration, trust in scientists, and delegation of resources; countries with neopatrimonial regimes like North Korea, where power derives from networks of personal loyalty, tend to be especially poor managers of nuclear programs. These regimes are prone to meddling in scientists’ activities and can threaten execution for failure. Saddam Hussein’s Iraq had multiple siloed efforts to produce nuclear material, but he so terrorized his scientists that they made almost no headway for a decade. Yet despite being a poster child for this type of regime, and being particularly brutal and ruthless dictators, Kim Jong Un and his father, Kim Jong Il, not only acquired nuclear weapons but also made rapid advances in their program. One prominent scholar predicted that North Korea’s regime relegated it to forever pursuing nuclear weapons at a “snail’s pace,” if at all. That snail is now clearly a hare. 3. Vulnerable states can be deterred or denied As a relatively weak state under intense international scrutiny, North Korea should have been deterred or simply blocked from brazenly acquiring and testing nuclear weapons, especially in the face of American and allied military threats. North Korea faced a deadly serious threat of preventive war from the United States starting in the 1990s, and while it is easy to dismiss such threats as lacking credibility due to Pyongyang’s ability to retaliate against Seoul, Kim Jong Il apparently did believe US threats of force in 1993 and 1994 were credible, and these threats were followed by the Agreed Framework in 1994, which temporarily froze North Korea’s plutonium program. But North Korea learned from this experience, hiding and dispersing its program better, rendering the threat of successful preventive strikes even less credible. Over time, North Korea was seemingly emboldened by the threat of US military action, openly testing missiles and eventually nuclear weapons in defiance of not just the United States but its erstwhile patron China. So if experts were wrong about all that, what does explain North Korea’s nuclearization? A couple academic theories do a better job at explaining this outcome. Indeed, the oldest theory in the book—which holds that states that perceive severe threats will bear high costs to acquire nuclear weapons—may help explain North Korea’s success despite a crumbling economy. As the late realist Kenneth Waltz once argued: “no country has been able to prevent other countries from going nuclear if they were determined to do so.” Yet there is something fundamentally unsatisfying about this argument: It suggests, at heart, that stopping highly motivated proliferators is a hopeless task. Fortunately history shows that’s not the case: The United States has prevented a handful of countries, even those in their own dire security environments, from acquiring nuclear weapons, such as South Korea, Taiwan, West Germany, Iraq, and Iran. A more complete explanation would account for why North Korea was able to weather harsh international pressure from the United States and its partners, while other similarly threatened countries were not. Here, theories that focus on North Korea’s economic orientation and its ability to maintain the support of key allies do a better job. As a hypernationalist regime with a state-managed, closed economy, North Korea had relatively little to lose from international pressure. As an influential 2007 study argued, these types of regimes face low costs from sanctions—since they aren’t economically integrated to begin with—and in fact they may relish a nuclear weapons program as a tool for bolstering nationalist myths. North Korea was particularly immune to unilateral sanctions levied by the United States, as it had virtually no political or economic ties to Washington even before it began pursuing nuclear weapons. The fact is though that North Korea has never been entirely impervious to outside forces. In particular, Pyongyang has relied on the economic and political support of China, especially since the fall of the Soviet Union—Kim Jong Un’s defiant assertion of independence from Beijing is only occurring now. If a country’s key patron is willing to look the other way and limit any sanctions to token measures—and indeed, increase trade as international sanctions ramp up—this provides shelter that can facilitate the acquisition of nuclear weapons. Similarly, America’s willingness to look the other way helped give Pakistan the space to acquire nuclear weapons three decades ago. North Korea’s ability to defy expectations might seem like cause for pessimism. After all, if a country as poor and backward as North Korea can do it—under the constant threat of sanctions and military action—a better question may be not who can acquire nuclear weapons, but who can’t? Nevertheless, we can and should draw useful lessons from North Korea. It seems time to put to bed a couple of theories as comforting myths. We now know that countries with weak economies can eventually master nuclear or missile technology. Chinese, Indian, and Pakistani acquisition of nuclear weapons already suggested as much, but the North Korean example has made it clear once and for all. Nuclear technology is old, many components are readily available and masterable, and smart determined states can stay one step ahead of the international community with even a little breathing room. We should also stop assuming that even the most pathological and brutal dictators can’t manage these programs successfully. North Korea may be an outlier, in many ways…so far. But it may not be for long, and our policies need to be updated to internalize the lessons of North Korea’s odds-defying acquisition of nuclear weapons. Nonproliferation efforts relying primarily on export controls and efforts to limit technology may buy time but are clearly insufficient against a motivated proliferator. Policies that depend on hoping for the regime to fail or fall are misguided in a world where impoverished dictators can indigenously master nuclear technology. To be successful against isolated countries like North Korea, nonproliferation policies must either address the proliferator’s underlying motives—in other words, their sense of insecurity—or they must enlist a strong multilateral coalition that enforces sanctions vigorously, with few exploitable cracks. This is a tall order, but North Korea shows that the stakes are rarely higher.