Nuclear terrorism: US officials say it’s best to plan for the worst

In a recent Bulletin article, “Would terrorists set off a nuclear weapon if they had one? We shouldn’t assume so,” Christopher McIntosh and Ian Storey offer a provocative challenge to what they term the “acquisition-use assumption,” which holds that non-state actors who attain a nuclear capability would almost certainly conduct a nuclear attack as quickly as practicable. The authors argue that although this worst-case scenario is certainly possible, terrorists who obtain a nuclear device could pursue a range of other strategies, such as nuclear blackmail, that do not involve immediate detonation. They suggest that the study of terrorist doctrine and historical behavior offers insights into potential alternative uses of a nuclear capability that terrorists might deem more strategically advantageous. Policy makers, the authors write, should look beyond the worst-case scenario and plan for these other contingencies.

It is true that the acquisition-use assumption is prevalent among US policy makers and that it motivates a wide range of activities to prevent terrorists from acquiring a nuclear device. However, the implication that this assumption stems from ignorance of the vast literature on terrorist thinking and strategy is incorrect. There is, in fact, a very good reason why policy makers would consciously exercise extreme conservatism in their assessment of the nuclear terrorism risk and why they would organize nuclear security policies around a “single, worst-case version of a threat” despite alternative possibilities. Indeed, while terrorists in possession of a nuclear device would have many options beyond its immediate detonation, the US strategy to deny them a weapon in the first place by definition eliminates each of these additional opportunities.

As an academic exercise, there is often value in challenging entrenched beliefs, especially when the failure to do so causes useful insights to be ignored. McIntosh and Storey suggest that discarding the acquisition-use assumption enables “planning for more tailored responses for a range of outcomes.” For example, they argue that “pressure points” exist that can be used to discourage a nuclear-capable terrorist group from going forward with an attack, including influencing terrorists’ public support and sources of financing. These approaches certainly deserve careful study. However, assuming the worst about terrorist intentions and planning for various non-use scenarios are not mutually exclusive. The latter can be done inexpensively by a relatively small group of people, and the authors present no evidence that the acquisition-use assumption actively inhibits such study.

Further, while McIntosh and Storey identify costs to this seeming myopia, they do not acknowledge any conceivable benefits. In particular, by studying the acquisition-use assumption purely in the abstract, the authors fail to consider its catalytic effect on global nuclear security efforts. Where they see unimaginativeness in this assumption, national security professionals see a simple, arresting principle that crystallizes the enormity of the consequences if terrorists were to obtain enough material for even a single nuclear device. This recognition in turn helps galvanize the costly and intensive work necessary to protect nuclear material from illicit acquisition worldwide. That the acquisition-use assumption is so uniformly shared across highly dissimilar governments, many otherwise inimical to US priorities, suggests that the conclusion is not born of ignorance but arrived at logically.

Nonetheless, even if the authors are correct that terrorists may not reflexively detonate a nuclear device, their conclusion is hardly reassuring. Of the four alternatives to outright detonation they describe—nuclear blackmail, opacity, latency, and dormancy—none is tolerable to the world order. In a blackmail scenario, for instance, any conditions that terrorists attach to the non-use of a nuclear weapon would likely be radically unacceptable to the United States and its allies. Even a deterrence paradigm, where terrorists refrain from use as long as they are able to operate unmolested, would be intolerable. This arrangement would allow a group like ISIS to establish a geographic caliphate under the immunity of a nuclear deterrent, where it could tyrannize the population under its control, potentially plan and launch attacks against the United States, and expand its territorial holdings. Further, even a group that judiciously withheld the use of a nuclear weapon could always change its mind, holding the world hostage to the whims of its leaders indefinitely.

In their eagerness to transpose lessons from the “rich history of deterrence and nuclear strategy” to the study of nuclear terrorism, McIntosh and Storey overlook that such an exercise would not be an unvarnished good. During the Cold War, a number of strategists challenged the widespread belief that a nuclear war between the United States and the Soviet Union would be apocalyptic and that any notion of prevailing in such a conflict was madness. With proper planning and investment, some argued, the United States could achieve an outcome in a nuclear war that, while tragic, was nonetheless distinguishable from several inferior alternatives. Such thinking was hotly criticized on the grounds that it might normalize the idea of nuclear conflict and thus make war more likely. Many preferred the simplicity of the conclusion Ronald Reagan reached—that “a nuclear war cannot be won and must never be fought.” Similarly, by entertaining scenarios in which terrorists’ acquisition of a nuclear weapon may not result in calamity, policy makers may lose the sense of urgency that has propelled more than a quarter century of effort to stave off such an event.

The United States’ approach to preventing and combating nuclear terrorism is best described as a “defense-in-depth” strategy that requires adversaries to defeat multiple layers of security to successfully obtain and detonate a nuclear device. As scholar Michael Levi observes, “It has often been said that defense against terrorism must succeed every time, but that terrorists must succeed only once.” While this is correct from plot to plot, he notes, the logic is reversed within each individual plot: “Terrorists must succeed at every stage, but the defense needs to succeed only once.” The key to US nuclear counterterrorism strategy is therefore to create multiple chokepoints through which terrorists must pass to achieve a nuclear capability, each of which provides an opportunity to detect, disrupt, and defeat them. These opportunities span the full life cycle of a terrorist nuclear program, from assembling expertise and technical data to attempting to acquire nuclear material and technology and finally to transporting the material or device to the target.

Although there is no reason to believe that any terrorist group today possesses a nuclear weapon or even an organized program to obtain one, several groups have been unambiguous about their desire to achieve this capability, presenting an enduring challenge to international security. And while building a nuclear device would require substantial resources and advanced technical skill, policy makers cannot assume that these impediments will hinder terrorists forever. The only failsafe means to ensure that non-state actors do not acquire the world’s most lethal capabilities is to prevent their acquisition of weapons-usable nuclear material.

Consequently, the United States administers an array of nuclear security and counterterrorism programs to place these materials and associated technology and information far beyond the reach of terrorists. Over the past three decades, the United States has removed, eliminated, downblended, or confirmed the disposition of over 20,000 kilograms of highly enriched uranium and plutonium from 48 countries and Taiwan—enough material for thousands of nuclear weapons. The United States has also worked with foreign partners to convert (or verify the shutdown of) over 100 research reactors and isotope production facilities from the use of highly enriched uranium to low enriched uranium, reducing the need for commercial applications of uranium enriched beyond 20 percent. The United States also works to improve the security of its foreign partners’ nuclear facilities, providing security system upgrades, funding programs to mitigate insider threats and improve transportation security, and conducting training to strengthen regulatory regimes, security culture, and cybersecurity.

Securing nuclear materials not only protects them from theft but also discourages terrorists from attempting to steal them in the first place, an effect termed “deterrence by denial” in the lexicon of nuclear strategy. Yet, the more familiar form of deterrence—dissuading an adversary by threat of retribution—is also operative in this context. Although terrorist fanatics may not fear the loss of life or territory in a US retaliation, potential state sponsors of nuclear terrorism in all likelihood do. The United States therefore makes substantial investments in nuclear forensics capabilities, allowing officials to attribute the source of any nuclear material interdicted outside of regulatory control or used in a terrorist nuclear attack. These tools allow the United States to credibly threaten reprisal against any state that provides nuclear material to terrorists. Indeed, the 2018 Nuclear Posture Review pointedly warns adversaries that abetting a terrorist nuclear attack against the United States would qualify for “the ultimate form of retaliation,” whose meaning should be unmistakable.

The US intelligence community constantly monitors for indications of terrorist interest in nuclear weapons. This vigilance supplies information that allows the United States to prioritize the most dangerous terrorist efforts for neutralization. Should terrorists somehow gain possession of nuclear material, the next line of defense consists of the constellation of radiation detection technologies that have been deployed around the world to interdict smuggled nuclear weapons and materials. The United States has worked with foreign partners to distribute this equipment to more than 60 countries. Just as importantly, the United States has built enduring relationships in these countries to counter nuclear smuggling.

Domestically, roughly 57,000 radiation detectors are in operation, from portal monitors that scan bulk cargo at seaports to hand-held devices operating at border crossings and throughout the US interior. If terrorists managed to overcome these many obstacles, they would still have to contend with the last line of defense—highly mobile nuclear incident response personnel who can search for a nuclear device based on a variety of signatures. Once a device is interdicted, highly skilled teams distributed across the country are equipped and trained to characterize and defeat the device.

Although the breadth of this architecture is impressive, the strong US preference is not to neutralize a nuclear threat at the last possible moment. Securing nuclear materials at their source remains the most effective way to prevent a terrorist nuclear attack—or the range of other outcomes that McIntosh and Storey describe. Here much work remains to be done.

More than 20 states continue to possess highly enriched uranium and separated plutonium stored at hundreds of facilities with varying degrees of security. As part of an effort to strengthen nuclear security worldwide, the United States continues to advocate for universal membership in and compliance with the Amended Convention on the Physical Protection of Nuclear Materials, the international convention to ensure the protection of nuclear materials and facilities. The convention stipulates requirements for protecting nuclear materials, including civilian materials, in domestic and international use, storage, and transport. As of late 2019, close to 40 states that are party to the original convention have yet to ratify the amendment, and many that have done so have yet to fully implement its provisions.

McIntosh and Storey should be commended for the creativity of their insights on the threat of nuclear terrorism and their willingness to challenge a particularly hardened example of conventional thinking. Although the subject of nuclear terrorism, like the long-running debate about deterrence and nuclear strategy, may inspire pointed disagreement, it is crucial that this threat not recede from our imagination. Continued focus, analysis, and action are necessary to ensure that terrorists are never able to use or threaten to use nuclear weapons against innocent people. Any outcome short of that standard will represent a policy failure with few parallels in modern history.