► Each U.S. presidential administration puts its own stamp on nuclear declaratory policy, which involves a written description of how it understands the role of the nuclear arsenal.

► The present debate concerns whether to retain a version of “calculated ambiguity,” or whether to adopt a narrower account of how nuclear weapons fit into national-security policy.

► The practical implications of declaratory policy are outweighed by the realities of how the U.S. nuclear arsenal is managed.  

Like a strange flock of migratory birds, the subject of nuclear declaratory policy returns to U.S. policy debates reliably once per presidential administration. The precise timing depends on when each administration conducts a nuclear posture review (NPR). While Congress has sometimes mandated such a review, the Biden Administration has undertaken this procedure voluntarily. The results of the Biden NPR are expected to become public early in 2022, in conjunction with the release of a new national security strategy.

Declaratory policy also predictably stirs passions among nuclear policy specialists, although the reasons why aren’t immediately obvious. This arena involves words alone: carefully drafted paragraphs to be recited by senior officials charged with explaining the role of nuclear weapons in national policy, including how, where, and when they might or might not be “employed.”

On the surface, declaratory policy statements balance the needs of deterrence with the needs of reassurance and legitimation. Deterrence is understood to occur in the mind of an enemy; if the foe is to be made to reconsider a course of action by fear of the consequences, they must be made to have an appreciation of the consequences. But threatening messages are also routinely accompanied by soothing messages in the form of “negative security assurances.” This generally consists of language pledging not to wield nuclear weapons against countries without their own nuclear arms, indicating that the United States is a sane and responsible country, so there is no need for most other states to be concerned about its nuclear arsenal.

Negative security assurances are generally not controversial. In both the Obama NPR of 2010 and the Trump NPR of 2018, this language consisted of the same sentence: “The United States will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the Nuclear Non-Proliferation Treaty (NPT) and in compliance with their nuclear non-proliferation obligations.” Using different language, both documents also indicated that the United States could modify this assurance if non-nuclear forms of attack were ever to become sufficiently threatening.

Where controversy emerges is around the language describing when nuclear weapons might be used. The two major parties have begun to diverge on this point. In 2010, the Obama NPR offered the following statement: “The fundamental role of U.S. nuclear weapons, which will continue as long as nuclear weapons exist, is to deter nuclear attack on the United States, our allies, and partners.” Secondary roles also exist, but the improvement of other military capabilities means that “the role of U.S. nuclear weapons to deter and respond to non-nuclear attacks—conventional, biological, or chemical—has declined significantly.” The existence of this “narrow range of contingencies” meant that the United States could not yet “adopt a universal policy that deterring nuclear attack is the sole purpose of nuclear weapons,” although it would seek to “establish conditions” permitting such a change in the future.

The 2018 Trump NPR pointed to similar if somewhat wider range of threats that might merit a nuclear response. It stated that the United States “would only consider the employment of nuclear weapons in extreme circumstances to defend the vital interests of the United States, its allies, and partners. Extreme circumstances could include significant non-nuclear strategic attacks. Significant non-nuclear strategic attacks include, but are not limited to, attacks on the U.S., allied, or partner civilian population or infrastructure, and attacks on U.S. or allied nuclear forces, their command and control, or warning and attack assessment capabilities.” While the Trump NPR conceded that the “highest U.S. nuclear policy and strategy priority is to deter potential adversaries from nuclear attack of any scale,” it also insisted that “deterring nuclear attack is not the sole purpose of nuclear weapons.”

One might ask how much difference truly exists between “fundamental role” and “highest priority.” The tone and emphasis of the two documents certainly differ, and the 2018 NPR’s language contains noteworthy language about attacks on nuclear command and control or warning and attack assessment capabilities. But the deeper differences between the two camps come into view when considering the future.

For the drafters of Obama’s NPR, the proper goal of nuclear policy was to continue to “reduce the role of nuclear weapons” in deterring non-nuclear attacks. This stance was consistent with President Obama’s famous speech pledging to “seek the peace and security of a world without nuclear weapons.” After all, if all nuclear-armed states were someday to agree that their nuclear arsenals existed only to deter the use of each other’s nuclear weapons, then a path to global nuclear disarmament might be found. The wording in the 2010 NPR also echoes a commitment made by America, Britain, China, France, and Russia at the NPT Review Conference held in 2000: they would pursue a “diminishing role for nuclear weapons in security policies to minimize the risk that these weapons ever be used and to facilitate the process of their total elimination.”

There is no hint of these high-minded sentiments in the Trump NPR, which simply treats nuclear weapons as a fact of life. Among the purposes of the U.S. nuclear arsenal, it declares, is to “hedge against prospective and unanticipated risks.” The “uncertainties of the future threat environment” require an arsenal that can adapt to the emergence of new nuclear-armed adversaries, the rapid expansion of existing adversaries’ arsenals, or even “unexpected technical risks throughout the life cycle of U.S. nuclear capabilities.” This language implies a need for redundancy within the nuclear stockpile, suggesting relatively little room for further reductions. Disarmament, furthermore, could not be entertained without first achieving a “transformation of the international security environment”—something for which no obvious path presents itself.

The present debate

Since the end of the Cold War, the overall pattern of declaratory policy has conformed to the idea of “calculated ambiguity.” Washington’s decision to sign the Chemical Weapons Convention in the early 1990s and to commence the destruction of its chemical stockpiles raised the question of how it might respond to chemical attacks from an enemy that had not done so, such as North Korea or perhaps Syria. Some experts believed that Saddam Hussein’s Iraq had refrained from using its chemical and biological weapons in 1991 only because of the prospect of nuclear retaliation. But it was also recognized that nuclear weapons are vastly more destructive than these other sorts of “weapons of mass destruction,” and it is uniquely impossible to shield large numbers of people from their effects. Nuclear effects are simply of a greater magnitude, well out of proportion to the threats posed by weapons like sarin, VX, or aerosolized anthrax. The result was a compromise. The United States does not rule out nuclear retaliation against chemical or biological attack. But since this threat would not be highly credible, it also does not promise it. Whatever this stance achieves, it achieves through ambiguity.

Some American nuclear policy experts soon grew dissatisfied with this idea and have recommended the adoption of a “no first use of nuclear weapons” pledge, or NFU, in its place. NFU, which has been China’s stance since it tested its first nuclear device in 1964, is a categorical pledge never to be the first to use nuclear weapons. By possessing nuclear weapons of its own, Beijing has explained, it can prevent its enemies from undertaking a policy of “nuclear blackmail,” or using the threat of nuclear attack for coercive purposes. NFU meant that China itself would not engage in these practices. For many American experts, including this author, the idea of NFU has been attractive because a credible promise not to strike first would enhance stability. If two nuclear-armed opponents became confident that the other side was not contemplating a nuclear attack, then neither would have to consider whether to execute a preemptive strike. Nuclear war would become less likely. By the same token, ambiguity about willingness to strike first could invite the possibility of a preemptive nuclear attack.

According to Fred Kaplan’s book The Bomb: Presidents, Generals, and the Secret History of Nuclear War, the Obama Administration debated on two separate occasions whether to adopt an NFU policy, ultimately setting it aside in favor of the declaratory policy described in its 2010 NPR. NFU suffers from some credibility problems of its own. Especially if a country faces an opponent like the United States or Russia, with a large nuclear arsenal kept on continuous alert, it might not be willing to rule out being attacked simply because of a verbal assurance. NFU might do no harm, but it also might not achieve the intended benefits.

Another concept, “sole purpose,” famously appeared in the 2010 NPR as an option not selected and as a goal for the future. In January 2017, in the last days of his vice presidency, Joe Biden endorsed this idea in public remarks. He went on to include it in his 2020 presidential campaign platform. Opponents of the idea frequently lump it in with NFU, but it would be better understood as falling somewhere between NFU and calculated ambiguity. Instead of offering a specific pledge of restraint, it would simply cite nuclear deterrence as Washington’s reason for continuing to possess nuclear weapons of its own. Potential enemies would be left to draw their own conclusions about how an American president might respond to various forms of attack.

Despite President Biden’s own stated preference, a recent news report in Politico claims that the nuclear posture review being prepared by the Department of Defense may not offer him the option of including a “sole purpose” declaratory policy in the final document. Earlier reports in the Financial Times and the Washington Post cited opposition from key U.S. allies as a reason to avoid making a change in this direction. The decision, regardless, will fall to the president himself.

The disconnect

The irony of these declaratory-policy debates, which currently overshadow all of the material aspects of nuclear posture in news coverage, is how disconnected they are from the realities of how the U.S. nuclear arsenal is managed. If one were to inquire after the de facto U.S. nuclear policy, apart from whatever official documents might say, the correct answer would be something close to sole purpose. One might could even call it “no use of nuclear weapons—until and unless the president decides otherwise.”

It is no accident that no nuclear weapons have been used in war since 1945. The bombs dropped on Hiroshima and Nagasaki were done almost as a matter of ongoing routine, the latest development in the air war against Japan’s cities. The historian Alex Wellerstein has found that President Truman was informed of the plans for their use in only the most general terms. After the bombing of Nagasaki, he issued a specific instruction that no further nuclear weapons be used without his specific, personal authorization. This has been the prevailing pattern ever since.

The president’s decision to retain exclusive authority over the decision to use nuclear weapons has has two important implications, which recurring debates over declaratory policy too often obscure.

First, no standing verbal formula can prevent a president from exercising this authority. It lacks any binding force upon the commander-in-chief. More sophisticated academic discussions of declaratory policy address this point, usually explaining that whatever restraint it may produce derives from “audience costs”—that is, a president’s concern for their reputation. If ever a scenario did arise that was truly dire enough to warrant consideration of using nuclear weapons, then it is hard to imagine that audience costs would loom too large.

Second, and perhaps more subtly, military leaders would be poorly advised to assume that any president would be willing to go first, whatever their top generals might recommend. As a practical consequence, the drafters of war plans should not assume that nuclear weapons will be available to them. Under the present system, only the president decides.

Occasionally, senior officials will deviate from formal declaratory policy and simply explain some version of this reality. In 2020, Air Force General John Hyten, the Vice Chairman of the Joint Chiefs of Staff and the previous commander of U.S. Strategic Command, recounted to CNN that he had found it necessary to reassure his counterparts in Britain and France that the United States, by reducing the explosive yield of some of its nuclear warheads, was not preparing to fight a limited nuclear war. “I strongly believe… that [deploying lower-yield weapons] actually deters Russia from using nuclear weapons, and the point I made to both our allies from both Britain and France is that the sole reason we have nuclear weapons is to prevent others from using nuclear weapons.”

For non-nuclear-armed allies of the United States like South Korea, Germany, or Japan, the practical implications of changes in U.S. declaratory policy would be essentially nil. As the story related by Gen. Hyten suggests, what allied defense policymakers dislike most are any changes to the status quo. Changes may require explanations, and there are fewer things that policymakers are less comfortable with than explaining nuclear weapons issues to their own public.

Reasons for change

Why should an administration be concerned with making adjustments to declaratory policy that have so little material bearing on either deterrence of adversaries or assurance of allies? The best answer lies beyond questions of deterrence or assurance. Rather, it concerns whether to keep faith with promises to reduce the role of nuclear weapons in national security, and the consequences of failing to do so.