The U.S. State Department’s Office of the Undersecretary of State for Arms Control and International Security on April 24, 2020, published online a paper entitled “Strengthening Deterrence and Reducing Nuclear Risks: The Supplemental Low-Yield U.S. Submarine-Launched Warhead.” Christopher Ford, the de facto undersecretary, authored the introduction, while the section on “The W76-2 Low-Yield Option” was attributed to the Bureau of Arms Control, Verification, and Compliance.

Briefly, the paper describes why and how the 2018 Nuclear Posture Review (NPR), issued under U.S. President Donald Trump’s administration, clarified “‘the extreme circumstances’ under which the United States does not a priori rule out the possibility of using nuclear weapons.” The paper adds further that “deterring limited nuclear attacks on allies and deployed U.S. forces” is the most urgent nuclear deterrence challenge today. To this end, the United States should continue to deploy the W76-2 low-yield nuclear warhead on submarine-launched ballistic missiles (SLBMs). In explaining this controversial position, the paper respectfully addresses the central arguments that have been made against this weapon.

Like previous writings by Ford, this one will engender intense debate among nuclear policy aficionados in the United States and around the world. Carnegie Vice President for Studies and Ken Olivier and Angela Nomellini Chair George Perkovich, as before, welcomes the insights that the State Department publication provides into U.S. policy and offers the following critique of the paper in hopes of inviting others to join this discussion.

Clarifying the 2018 Nuclear Posture Review, Sort Of

Much of the debate on the new paper will focus specifically on the case Ford and his colleagues make for deploying the low-yield W76-2 nuclear warhead. Yet, while that argument is important, Ford’s introductory explanation of the 2018 NPR deserves more attention.

George Perkovich
Perkovich works primarily on nuclear strategy and nonproliferation issues; cyberconflict; and new approaches to international public-private management of strategic technologies.
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Ford writes that a major “innovation” of the NPR was “the greater clarity we brought to U.S. declaratory policy by specifying that the ‘extreme circumstances’ under which the United States does not a priori rule out the possibility of using nuclear weapons include the threat of ‘significant, non-nuclear strategic attacks.’”

This is very interesting. Previous Republican and Democratic administrations have declared “extreme circumstances” to be the threshold whereupon the United States would consider using nuclear weapons. Now a senior Trump administration official says this phrasing is excessively ambiguous. He is correct.

More importantly, by using a double negative (“does not . . . rule out”), Ford is suggesting declaratory policy should not convey when the United States would be justified in using nuclear weapons. Rather, he’s saying that U.S. nuclear use is ruled out except under “extreme circumstances” that should be clarified. In an actual war, the semantic shift probably would mean nothing, but the nod toward a nuclear taboo should be welcomed. Whatever the motivations, it is useful to have a Republican administration on record in this way.

The focus of analysis and debate should then shift to clarifying what such extreme circumstances could be. Here, Ford writes, the inclusion of “significant, non-nuclear strategic attacks . . . did not expand the range of circumstances in which the United States might use nuclear weapons. . . . No previous U.S. administration . . . had been willing to offer any insight into what such longstanding comments about ‘extreme circumstances’ actually meant. . . . We opted for honesty and for clarity in order to enhance deterrence and reduce the risk of miscalculation.”

Greater clarity is indeed welcome. The 2018 NPR did not provide much, but Ford’s introduction might offer more. What would make a non-nuclear strategic attack “significant” enough to overcome the United States’ generally ruling out nuclear use?

Ford answers: “This declaratory policy clarification was necessary because ours is an age in which non-nuclear capabilities have the potential to wreak havoc in some respects comparable to a nuclear attack [emphasis added].” Merriam-Webster defines havoc as “wide and general destruction” or “great confusion and disorder.” If Ford wished to convey the first meaning, why not just say something like “death and destruction”? Here, the qualifier, “havoc in some respects comparable to a nuclear attack” becomes very important. Perhaps Ford and the administration are thinking of cyber attacks, which could cause great confusion and disorder but would not be violently destructive and lethal. If so, why not say it?

A leaked draft of the 2018 NPR declared that cyber attacks against critical civilian infrastructure could justify U.S. nuclear use. But the final version of the document dropped this specific reference, which had become controversial. A cyber attack that corrupted the integrity of financial data of one of the world’s global systemically important financial institutions over several weeks or months and that was publicly revealed by its perpetrators to cause massive confusion, economic loss, and political disorder would fit the definition of havoc. But would it be comparable enough to nuclear attack to warrant U.S. nuclear use? What about shutting down a regional electrical grid?

One of the strategically attractive things about cyber attacks is that they don’t necessarily cause destruction or even irreversible damage, let alone death. Assume that the United States could with 99.9 percent certainty attribute a cyber attack to the Kremlin (and not merely Kremlin proxies). Would it be legally and strategically justifiable to respond by attacking Russia with nuclear weapons? What if China or North Korea were the villain in the same scenario? Nuclear retaliation would not stop the cyber attack or cause the adversary to retreat. Nor would it spare the United States or the world from death and destruction; it would add to it if the adversary then used nuclear weapons too.

Nuclear attack (against most targets) means death and destruction, perhaps on a massive and indiscriminate scale. Thus, using nuclear weapons in response to an adversary attack (of whatever sort) that caused death and destruction equivalent to a nuclear attack could meet legal criteria as well as traditional security thresholds. It is important to recall here that, in Ford’s words echoing the 2018 NPR, “U.S. nuclear operations would adhere to the law of armed conflict.” (The International Court of Justice in 1996 issued an advisory opinion that while many uses of nuclear weapons would violate international law, it could not “reach a definitive conclusion as to the legality or illegality of the use of nuclear weapons by a State in an extreme circumstance of self-defence, in which its very survival would be at stake.”) But, if a non-nuclear strategic attack did not cause massive death, would it be nevertheless “in some respects” comparable to a nuclear attack? What scale of physical destruction crosses this threshold?

Clarity in nuclear policy is good. There is still a lot more work to do in defining a non-nuclear cause of “havoc” that would be comparable enough to nuclear attack to make it sensible and legal for the United States to respond by using nuclear weapons. Perhaps in 2021 a new administration, whoever heads it, should produce a new or revised Nuclear Posture Review adding still more clarity to that which the State Department has tried to provide.

Why Maintain Massive Strategic Arsenals of High-Yield Weapons?

“While we continue to posture our forces to deter large-scale nuclear attacks,” the State Department paper declares, “the 2018 NPR also highlighted the importance of deterring limited nuclear attacks on allies and deployed U.S. forces—something both the Obama and Trump Administrations considered more likely than a ‘bolt-out-of-the-blue’ attack.”

Because “bolt-out-of-the-blue” attacks are very implausible, the primary role of nuclear weapons today is to deter escalation of potential Russian and Chinese conflict with U.S. allies. To this end, the State Department paper argues that there is a need for low-yield nuclear warheads that are not forward deployed. The specific arguments for the SLBM-based low-yield W76-2 warhead are discussed immediately below. Here, I largely endorse the general proposition in favor of low-yield nuclear weapons (compared to high-yield ones) and draw a larger conclusion that both the Trump administration and many of its critics ignore.

The main argument for a survivable low-yield option is that it is “capable of providing an effective response with less collateral damage than a very high-yield weapon.” Thus, “potential adversaries may perceive it as a more credible response to a limited attack and thus a more credible deterrent to a strategy that seeks to split the United States from its allies.” Low-yield weapons are advantageous insofar as they would cause less collateral death and environmental destruction than higher-yield weapons (on similar targets in similar numbers), which makes them less inconsistent with the law of armed conflict, which the United States has committed to follow.

But the State Department authors and, perhaps, many of their critics miss a huge implication of this argument: it calls into question why the United States “needs” an arsenal of more than 3,800 high-yield weapons. This does not imply politically infeasible unilateral nuclear disarmament. Rather, the point is that the State Department’s own facts and reasoning show that the United States (and the world) would be more secure against risks of catastrophic nuclear war and would have a more credible and law-abiding deterrent if it and Russia negotiated down the numbers and types of nuclear weapons suited for bolt-out-of-the-blue scenarios, and instead relied on a much smaller arsenal of low-yield weapons better suited to regional contingencies.

The enormous U.S. and Russian strategic arsenals of high-yield weapons are mostly targeted against each other in scenarios of rapid massive preemption and retaliation. These plans are as unrealistic and suicidal as the “bolt-out-of-the-blue” strikes that the State Department rightly dismisses. Everyone would be better off and deterrence would probably be more credible and certainly more legal if most of these weapons were bargained away. As Ford notes, “even though a low-yield nuclear weapon is less destructive than a very high-yield weapon, it is still capable of inflicting unacceptable costs.” Nuclear deterrence can survive the removal of overkill weapons.

Of course, to pursue such a course, both Moscow and Washington would need (for political reasons at least) China’s binding commitments not to build up its nuclear forces in ways that would threaten the new, less excessively threatening Russian and U.S. deterrents. The Trump administration has taunted China to join nuclear arms control, but it unfortunately has not even hinted what the United States and Russia would be willing to offer in return. The prospect of U.S. and Russian willingness to explore further major reductions in their nuclear forces in the direction suggested here could be a viable way to invite reluctant Chinese leaders to consider joining an arms control process. Such an approach likely would be applauded by non-nuclear-weapon states and international civil society. Chinese leaders then would need to decide whether their international interests would be better served by being seen as the obstacle to major progress in nuclear disarmament or instead being a facilitator of it.

The Low-Yield W76-2 Debate

The State Department correctly argues that it would not be credible (or desirable) to rely on use of “very high-yield warheads” to respond to Russian (or Chinese) use of limited numbers of lower-yield weapons in a regional war. Nor would it be desirable or feasible for the United States “to match Russia weapon-for-weapon at the non-strategic or theater level” by deploying “up to 2,000 ground-, air-, and sea-based non-strategic nuclear weapons.” As the paper notes, “A massive response to a limited attack is even less likely to restore deterrence and more likely to spur further nuclear escalation that could devastate the world.” (Interestingly, the paper does not add that such a massive response would be of dubious legality.)

The State Department correctly notes that the United States already has air-deliverable low-yield options in its arsenal and in development: “U.S. nuclear-capable bombers provide both penetrating and standoff response options; they are survivable against counterforce attacks when they are armed with weapons, alerted, and dispersed; and we can visibly signal with them in peacetime and military crises.”

“Yet,” the paper continues, “there are several distinct attributes of SLBMs that our air-based nuclear forces do not possess. Ballistic missiles are unmatched in their ability to reliably penetrate defenses. They are more prompt than air-delivered nuclear forces . . . [and] the low-yield SLBM provides a response option that is operationally survivable day-to-day and always ready. Thus, unlike our bombers and dual-capable aircraft, which are not armed, alerted, and dispersed day-to-day, we do not need to generate the low-yield SLBM in a crisis.”

However, to close, it is worthwhile to consider less adequate elements of the case for the W76-2. The authors acknowledge the widely discussed discrimination problem—that is, the difficulty Russian (or Chinese) early warning systems and personnel would have in distinguishing launched low-yield weapons from high-yield ones. Critics argue that Russia would be most likely to respond to this problem by assuming the worst and therefore could be more likely to unleash a more destructive response than advocates of the W76-2 assert. The State Department responds by saying a foe “would not be able to determine the yield of the weapons on a U.S. bomber or air-launched cruise missile either.” This seems correct and more like an argument for nuclear disarmament than anything else. More persuasive is the argument that “there is no strategic rationale for an adversary to use nuclear weapons in a limited way and then launch a massive nuclear attack upon detection of a single SLBM, triggering the unlimited war it is trying to avoid.”

Neither the State Department nor any other agency has articulated what the plausible targets of this weapon would be. The April paper says, “Our strategy for deterring limited nuclear war is not target-based; it is capacity based: we deter limited nuclear attack by sustaining an effective military posture to protect the vital interests of the United States and its allies in the face of nuclear-backed aggression.”

This does not clarify much, if anything. It raises as many questions as it answers. If there is an imperative to make plans for when deterrence fails, as the paper insists, then those plans must involve targets. What targets would SLBM-based low-yield nuclear warheads be needed to destroy that could not be adequately threatened by other low-yield weapons in the U.S./NATO arsenal? Without a sense of likely targets, it is extremely difficult for officials and analysts in the United States and elsewhere to assess whether these weapons are more likely to stabilize or destabilize crises and escalate or de-escalate nuclear exchanges.

Ultimately, given that the W76-2 is already deployed and U.S. allies do not seem to object to it, there is little, if anything, to be gained by removing it. Indeed, the administration and critics of this weapon are looking through the wrong end of the telescope. In focusing attention on the priority of deterring regional conflict and its escalation, the State Department’s paper makes a strong case for negotiating deep reductions in U.S. and Russian high-yield strategic weapons.