Like car brakes, nuclear arms control is easy to take for granted—until it fails. And, today, it’s failing badly. With the nuclear arms race back on, the world has no reliable brakes to reduce the damage of a catastrophic collision.

The arms control system that contained the volatility of the Cold War collapsed over the past two decades, as Russia violated and the United States abandoned a series of agreements that limited—and, in some cases, greatly reduced—both offensive and defensive nuclear capabilities. Most recently, U.S. President Donald Trump’s administration has threatened to let lapse in early 2021 a treaty governing long-range nuclear weapons.

Meanwhile, the United States broke the 2015 nuclear deal with Iran and the situation in North Korea remains moribund. Libya, which negotiated away its nascent nuclear program, was rewarded by having its leader impaled in a drainage ditch in the Sahara Desert. India and Pakistan, the two nuclear opponents who have recently come close to colliding, have not even attempted to negotiate limits on their growing arsenals.

The old arms control system cannot be rebuilt, but it can be reinvented to meet the tests of a fundamentally new era.

The old arms control agreements were hard to make, but the task of reinventing arms control in the twenty-first century will prove much harder. There are new players—China the most important among them—all of whom compete with and respond to one another. The escalation risks no longer come exclusively from familiar missiles but from new technologies with multiple uses that are harder to count and monitor from afar. These new technologies, which may be more tempting to use, will be entangled with nuclear systems in ways that severely complicate the challenge of deterring conflict and its escalation to and through nuclear war.

The old arms control system cannot be rebuilt, but it can be reinvented to meet the tests of a fundamentally new era. Beyond the logic of deterrence and the goal of reducing the probability of escalatory warfare, arms control should be guided by the imperative to limit the physical damage that could occur if deterrence fails. No two antagonists should wield weapons whose number and explosive power could not only destroy their own nations but also cast innocent bystander societies into catastrophe.

Bring in New Players

The first challenge will be to bring China into the arms control fold, a step that will reduce U.S. and Russian motivations to retain or even build up their already excessively destructive nuclear arsenals. Moreover, it would alleviate concerns that might otherwise drive China to expand and enhance its nuclear forces in ways that would fuel an arms race in Asia. China’s neighbors—especially Japan, South Korea, and Taiwan—would be reassured that they do not need to acquire nuclear weapons of their own to deter or potentially defeat Chinese aggression.

The first challenge will be to bring China into the arms control fold.

To overcome resistance, the United States and to some extent Russia will need to offer China clear benefits in return, which to date they have not. Even if China doubles its current stockpile of nuclear weapons, as the U.S. Defense Intelligence Agency warns, it would have less than one-seventh of the U.S. stockpile. China would also seek limitations on the missile defense systems the United States and its allies deploy in the future. To make this happen, Washington will need a bipartisan reconception of arms control’s objectives, giving greater priority to reversing arms races rather than winning them.

If China can be constructively engaged, these three larger nuclear powers would have a basis for urging India and Pakistan to begin negotiations around their own most destabilizing weapons, particularly if India perceives less of a threat from China. At that point, states armed with nuclear weapons could reassure those without them that they are trying seriously to fulfill commitments to end nuclear arms racing and pursue in good faith further nuclear disarmament. Preventing future proliferation depends on this.

Balancing New Weapons Technologies

Generating political will in Washington, Moscow, and Beijing is the first challenge in reinventing arms control. Then comes an even harder step: devising equations to value diverse, often asymmetric weapons systems. Balancing like-for-like long-range ballistic missiles was akin to comparing American Peterbilt trucks to Russian KAMAZ trucks. Now, strategists and negotiators need to balance dump trucks against Ferraris, Teslas against boats, and satellites against planes.

The United States especially values its ballistic missile defenses. Interceptor missiles based on land in Alaska and California, at sea, or in space—and guided by suites of warning systems in space and on the ground—could now or in the future intercept missiles launched by Russia, China, or North Korea. Russia and China, however, fear that these defenses could embolden the United States to conduct first strikes on their nuclear deterrent systems (because U.S. missile defenses would then block whatever missiles were not destroyed in the strike). The 1972 Anti-Ballistic Missile Treaty managed this problem for the United States and Russia but, since the 2002 U.S. withdrawal from the treaty, Russian and Chinese defense analysts have insisted that limiting missile defenses would be a necessary prerequisite to limiting or reversing the modernization and potential expansion of their offensive nuclear arsenals. Yet the United States has adamantly rebuffed them, especially as both countries have built up their inventories of nuclear and conventionally armed missiles. Even if the Republican Party’s opposition to limiting missile defenses could be overcome, negotiators would find it difficult to agree on an equivalence between defensive missile interceptors and offensive missiles.

Missile defense exemplifies the broader problem of entanglement, in which countries increasingly deploy non-nuclear means that are potentially capable of disabling an adversary’s nuclear weapons, even if their actual purpose is to counter the adversary’s conventional forces. The consequence could be inadvertent escalation resulting in nuclear use. U.S. early-warning satellites, for example, are used to detect an incoming nuclear attack on the United States and to cue forward-deployed missile defenses designed to intercept non-nuclear ballistic missiles. If Russia were losing a conventional conflict, it might attack these satellites to try to enhance the effectiveness of non-nuclear missile strikes against targets in Europe. From a U.S. perspective, however, Russian attacks against U.S. early-warning satellites—a lynchpin of its command-and-control system—could look like the prelude to Russian nuclear use. Indeed, in its 2018 Nuclear Posture Review, the Trump administration indicated it might use nuclear weapons in such circumstances.


Another manifestation of entanglement is dual-use weapons, which are capable of carrying either a nuclear or non-nuclear warhead. Every nuclear-armed state, except the United Kingdom, has such weapons. A military might fire a conventionally armed variant of a dual-use missile, but the adversary could easily interpret it as a nuclear attack—due to inherent ambiguity, technical error, or human misjudgment—and order nuclear retaliation. In this case, a nuclear war intended by neither side could nevertheless break out. And there’s no telling if or how a nuclear war could be kept limited (which is why reducing the destructive potential of arsenals is so important).

Innovative thinking and diplomacy will be necessary to figure out how the United States, Russia, and China (perhaps followed by India and Pakistan) can develop a mutually acceptable formula for balancing and limiting these multifaceted weapons and related tools of attack, including cyber weapons. Before any of these antagonists can negotiate with each other, they must first break down the bureaucratic and conceptual silos within their own militaries and civilian agencies to develop new models for stabilizing arms competitions.

The old standards of extremely high confidence in verification will have to be moderated.

This reinvention process will require new approaches to verifying the numbers and types of weapons each country says it has and its compliance with any agreed-upon limitations on them. The complexity and diversity of the weapons involved, and the reluctance of these governments to open themselves to intrusive inspections, mean that the old standards of extremely high confidence in verification will have to be moderated. Instead of limiting only a few readily observable technologies such as nuclear-only ballistic missiles, limiting a broader range of weapons and activities would allow confidence that at least some form of cheating would be detected and trigger previously agreed-upon investigation procedures—even if not all forms of cheating would be caught at once.

A New Clarity of Purpose

All of this is daunting—politically, technically, militarily.

One alternative is to simply prohibit the possession and use of nuclear weapons, as the 122 countries that adopted the Treaty on the Prohibition of Nuclear Weapons in 2017 set out to do. But the treaty does not explain how major security threats would be adequately addressed without nuclear weapons or how disarmament would be defined, verified, and enforced. In any case, none of the nine nuclear-armed states have signed it.

Powerful elements in the nuclear establishments of the United States, Russia, China, India, and Pakistan favor an antithetical approach. They seek military capabilities that would deny adversaries the reasonable hope of using nuclear weapons to win a war. But adversaries perceive those enhancements to be offensive, not defensive, so they build more weapons too. Such competitions entail great expense, produce instability, and carry unbounded potential for catastrophic destruction—not only for the nuclear antagonists but also, potentially, for many nonbelligerent nations.


Even if complete global nuclear disarmament is not feasible now, nuclear-armed states and the rest of the world would benefit from a renewed focus on reducing the dangers of nuclear war. A smaller survivable arsenal, like that of the United Kingdom, could still inflict such immediately massive damage that it would deter sane adversaries from risking aggression of the type that would justify their use. Old arms controls primarily sought stability through deterrence—removing each antagonist’s incentive to initiate the use of nuclear weapons. But the theoretical logic of deterrence can produce unending demands for more and “better” weapons. While maintaining deterrence is vital, the new goal should be more ambitious: bounding the level and spread of destructiveness if deterrence fails. Rational leaders will avoid situations that could lead to nuclear war, but multiple actors and entangled weapons technologies still risk inadvertent escalations up to and including nuclear detonations. The larger the arsenals and the more destructive their weapons, the greater the risk that their use will cause a global catastrophe.

The larger the arsenals and the more destructive their weapons, the greater the risk that their use will cause a global catastrophe.

Ensuring against catastrophic escalation should be the new organizing principle and goal of arms control. No two antagonists should wield weapons whose number and explosive power could not only destroy their own nations but also cast innocent bystanders into a nuclear winter—with sunlight blocked by stratospheric soot, global rainfall severely diminished, and agricultural productivity disastrously reduced. Even arsenals of less than 200 nuclear weapons—like those of the United Kingdom, India, Pakistan, North Korea, and perhaps Israel—could create more than enough destruction to deter rational decisionmakers. (There is no particular number that is likely to deter irrational leaders.)

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Because the United States and Russia have by far the largest arsenals, they must take the lead in reorienting the arms control conversation. A relatively easy way to start would be to update and expand studies by scientists in both countries during the 1980s to assess the probability that a nuclear war between them would produce a nuclear winter.

The dramatic improvements in computing power, atmospheric modeling, and climatic data in recent decades warrant an array of new studies, which would examine scenarios involving current and lower numbers of weapons, explosive power, and various types and locations of targets. If the United States and Russia were to lead by example in conducting such studies and inviting international scientific debate of declassified versions, other governments and international civil society organizations should be expected to urge China, India, and Pakistan to follow suit. The results could give all states a metric beyond deterrence theory for judging how much nuclear weaponry is enough and how much is too much.

In the near term, arms control must refocus on realistic goals. Bounding the physical destructiveness of nuclear war, should deterrence fail, is achievable; complete nuclear disarmament is not. Failing to do what can be done is tantamount to racing an explosives-laden truck down a steep hill without brakes. Citizens of the nuclear states—along with the rest of the warily watching world—deserve better.

  • George Perkovich