Effective counterforce impossible---adversaries can just retaliate later.

If the United States’ anxiety over nuclear terrorism is any guide, these requirements vastly overstate the threshold for credibility. After all, the fear that North Korea might transfer a nuclear weapon to terrorists has been central to the case for reversing its nuclear program. If these weapons pose a catastrophic threat in the hands of extremists, on what basis should they be considered less threatening when deployed by their original owners? In truth, Pyongyang can have confidence in its minimalist posture for two reasons. First, contrary to the emphasis placed on strategic delivery vehicles, such platforms are not necessary for nuclear retaliation. In extreme circumstances, a variety of unconventional delivery means can be used. As the late political scientist Kenneth Waltz observed, “Everybody seems to believe that terrorists are capable of hiding bombs. Why should states be unable to do what terrorist gangs are thought to be capable of?”43 Second, no arbitrary deadline exists for a state to respond to a nuclear attack. Retaliation may come weeks or even months after a first strike, providing ample time to prepare nondeployed warheads or even construct a makeshift weapon from available nuclear material. Together these concepts call into question the key assumption on which nuclear primacy rests: that a nuclear counterstrike must come immediately and in the form of ballistic missile attacks, or not at all. This questionable premise permits US leaders to entertain first strike scenarios that are wildly at odds with their apparent tolerance for risk.

Delayed—But Assured—Retaliation

During the Cold War, it was widely assumed that the United States and Soviet Union would launch a substantial portion of their arsenals the moment either believed itself to be under nuclear attack. Today retaliation may occur at a more plodding pace, in part because military imbalances are much more pronounced. A US first strike might virtually eliminate an enemy’s deployed weapons, requiring considerable time and effort for the state to respond. Additionally, delay is implicit in “no first use” policies, which commit a state not to use nuclear weapons except in retaliation for a nuclear attack. One such state is India, the nuclear strategy of which scholar Ashley Tellis describes as emphasizing “delayed—but assured—retaliation.” This posture reflects the belief that “for purposes of deterrence, the ability to retaliate with certainty is more important than the ability to retaliate with speed.”4

US planners’ dismissal of this posture generally centers on doubts about the “certainty” of assured retaliation. According to this line of thinking, no state can be completely confident of its second-strike capacity, especially if elaborate precautions are not taken to preserve it. Yet, this view conflicts with the basic premise of US counterterrorism policy, which emphasizes fissile material rather than assembled weapons as the most basic nuclear threat. As the National Research Council notes, lack of access to this material is the “primary impediment that prevents countries or technically competent terrorist groups from developing nuclear weapons.”45 Its mere possession, on the other hand, confers significant deterrent value even in nonweapon form. Indeed, Albert Wohlstetter, Gregory Jones, and Roberta Wohlstetter present the case of a state that is losing a short conventional war but possesses plutonium “in explosive concentrations” along with the “capability of assembling an implosion system.” In light of this combination, they write, “from the standpoint of the adversary who had been winning, it would be facing a government which to all practical effect had nuclear weapons.”46

By this standard, possession of fissile material alone ensures that a state can never truly be disarmed. Even after a highly successful first strike, the defender could use its surplus plutonium or highly enriched uranium to develop a crude retaliatory weapon, which it could then deliver using unconventional means. Only a small quantity of this material is needed, as US leaders frequently admonish. President Obama has warned that a mass of plutonium “about the size of an apple” would threaten hundreds of thousands of people.47 The International Atomic Energy Agency defines a “significant quantity” of plutonium—the approximate amount needed to produce a nuclear explosive device—as 8 kg.48 This unit of measurement should be kept in mind in any discussion of a disarming strike on China, which possesses roughly 1.8 tons of weapons-grade plutonium.49