There actually is some kind of Escalation Control Cabinet in the underground spaces beneath the Pentagon, but no one in the building thinks it holds the solutions to nuclear conflict.

Escalation control mechanism in the DC Metro’s Pentagon Station

While working deterrence policy under the Obama and Trump administrations, I never encountered a belief that there is any way to guarantee that escalation will remain limited if a conflict goes nuclear. Within the U.S. defense establishment, there is consistent understanding that even limited nuclear use between capable adversaries would bring grave risk of further escalation. Fortunately, planners and policymakers don’t conclude as a result that uncontrolled escalation is certain and that there is no point trying to limit the consequences if that awful day ever comes. In any nuclear conflict, there is a chance that efforts to limit escalation will succeed, and a chance that they will fail. Escalation control strategies reduce the likelihood of the worst possible outcomes if deterrence fails. Such strategies are also necessary to underwrite the credibility of efforts to deter conflict in the first place.

The Trump administration’s Nuclear Posture Review adopts a sound escalation control framework that incorporates two basic strategies: one aimed at limiting escalation in a conflict with the major nuclear powers, China and Russia, and the other tailored to threshold and minor nuclear powers. This framework decreases the likelihood of escalation in conflict by denying major nuclear adversaries confidence in their ability to win, while ensuring an ability to defeat minor nuclear powers. The current approach is effective and will remain so for many years, but only as long as a clearly discernible difference exists between major and minor nuclear powers. It will eventually require adjustment if North Korea’s nuclear capabilities continue to advance without careful changes to U.S. missile defense architecture. This article explores the differences between flexible response and escalation dominance, and explains why getting that distinction right — as the Nuclear Posture Review does — is crucial for avoiding the pitfalls of escalation dominance and maintaining an effective strategy.

Flexible Response and Escalation Dominance

There are two basic options for attempting escalation control. Both emerged early in the Cold War as the United States considered how best to respond to a Soviet ability to strike back with nuclear weapons. Each strategy plays a role in the Nuclear Posture Review’s escalation control framework.

Flexible response relies upon the ability to act at various levels of escalation to deny confidence in the adversary’s ability to win. Harold Brown explained it as “the ability to respond appropriately to any level of potential attack and to pose the risk of escalation to higher levels of conflict.” Originally, flexible response was NATO’s strategy for responding to Soviet aggression in Europe with something other than a world-ending massive nuclear counterstrike. Threatening massive retaliation to lesser attacks seemed less credible and therefore a less effective deterrent. Massive retaliation was also less desirable because it would assure greater destruction on all sides. The new Nuclear Posture Review continues a strategy of flexible response for countering the major nuclear powers, Russia and China. This includes a messaging element — simply telling each adversary that it cannot count on winning through escalation — and a capabilities element that involves ensuring the United States possesses “a range of limited and graduated options” for responding to Russian or Chinese escalation.

Flexible response discourages escalation by muddying the path to victory the adversary might envision. The idea that escalation may credibly elicit an effective countermove leaves the adversary asking, “If I ratchet the conflict up, then what happens next, and where will it end?” Flexible response gives both sides greater incentive to forgo further escalation. Possessing response options that are less escalatory also offers a way to potentially slow the conflict, providing additional time to find ways of stepping back.

Escalation dominance, on the other hand, relies upon superiority at various levels of conflict to ensure one’s own ability to win. According to Herman Kahn’s original formulation, escalation dominance “is a capacity, other things being equal, to enable the side possessing it to enjoy marked advantages in a given region of the escalation ladder.” The Nuclear Posture Review adopts escalation dominance only for countering minor and emerging nuclear powers where U.S. superiority is feasible across a wide escalation spectrum. The document never actually uses the term “escalation dominance,” but it promises, for example, that the United States has the capability and will to ensure that “there is no scenario in which the Kim regime could employ nuclear weapons and survive.”

Careful differentiation between flexible response and escalation dominance can help policymakers recognize when one strategy is sold or characterized in the other’s name. In particular, those who describe escalation dominance as the ability to threaten “a symmetrical and proportional response” or as a situation in which “[w]hatever move we make, he can match it and go further,” are more accurately describing flexible response. Similarly, policymakers should be wary of calls for dominance that explain what it takes to compete, but not what it would take to demonstrate clear superiority.

It is possible to view escalation dominance as a stronger form of flexible response rather than a distinct strategy, but there is an important conceptual distinction between casting doubt on the adversary’s ability to win and convincing him that he will lose if the conflict plays out.

What does this distinction look like in practice? If deterrence failure leads to military conflict between the United States and Russia, Russia’s leaders will have to decide whether to seek victory by engaging in more destructive forms of warfare. A successful U.S. flexible response strategy leaves Russia uncertain as to whether escalation would actually deliver victory, but confident that it would bring greater danger its own interests. Russia would then see three plausible outcomes: Russia wins, the United States wins, or things get out of control and everyone loses. Uncertain of which it would be, Russia is less likely to escalate.

In a conflict between the United States and North Korea, the Kim regime would similarly face a decision about whether to escalate. A successful U.S. escalation dominance strategy would mean the United States and its allies have the firepower to defeat North Korea in any type of conflict. Ideally, North Korea would then see defeat as the only plausible outcome. Confident that the United States possesses the means to prevail, North Korea is less likely to escalate.

However, it is important to remember that military superiority does not guarantee victory over an enemy that can continue to cause damage until its defeat is accomplished. A risk-accepting opponent might still escalate and gamble that the dominant side will concede rather than endure the costs of winning. Thus, even dominance cannot assure victory. Still, it does seem like the more reliable way of decreasing the likelihood of escalation. Yet prior to release of the new Nuclear Posture Review, Michael Fitzsimmons, a professor at the U.S. Army War College, urged American policymakersto resist “the false allure of escalation dominance.” Caution is indeed warranted, because dominance is hard to achieve and maintain.

The principal challenge of achieving escalation dominance is that it requires either the ability to fight at every level, or the ability to prevail at a lower level in the face of unmatched adversary escalation. Flexible response, by contrast, requires a range of options but not necessarily at every level. Superiority at some but not all levels is not true dominance because it does not fully mitigate the escalation pressures that dominance seeks to address. One side that can dominate at a higher level but not at lower levels, or that faces an opponent that can dominate at a lower but not at a higher level, will feel pressure to escalate. For example, a Russian perception that the United States can dominate a conventional conflict creates incentive for Russia to escalate to a level of nuclear employment, where it can compete better and may win. Incomplete superiority may instead be consistent with flexible response, since it would logically shake the enemy’s confidence but not ensure the ability to prevail.

The principal challenge of maintaining escalation dominance, on the other hand, is that it cannot be mutual and can therefore be unstable. Adversaries cannot both credibly proclaim escalation dominance because only one can possess the clear ability to prevail. Escalation dominance is thus stabilizing on shorter time scales of crisis or conflict, but potentially destabilizing over longer periods of military capability development and acquisition.

These difficulties should not exclude escalation dominance from strategy considerations. Instead, U.S. policymakers should understand that dominance is only viable for countering minor and threshold nuclear adversaries, like North Korea and Iran, that lack the capabilities and economic wherewithal to compete effectively. Only in such cases can the United States reasonably expect to maintain its competitive edge while avoiding undesirable arms-race dynamics.

Escalation Control Strategy in the 2018 Nuclear Posture Review

Flexible response and escalation dominance are each suited to countering a different class of adversaries.

Among major nuclear powers, dominance at the highest level of conflict is not an option because significant portions of deployed strategic nuclear forces can be made survivable, and defense against large-scale ballistic missile attack is not feasible. The competitive cost curve favors offense over defense, in that one can buy many strategic warheads for the cost of each effective interceptor. Furthermore, it is the absolute rather than relative effectiveness of defenses that determines the amount of damage ultimately suffered. Defenses that must be 90 percent effective against a minor power to prevent “unacceptable damage” may therefore need to be 99 percent effective against a major power.

With no effective defense against hundreds of Russian ballistic missiles, escalation dominance is not a real option for countering Russia. Superiority at lower levels is also out of reach. At the theater nuclear weapons level the NPR admits that “Russia possesses significant advantage … in non-strategic nuclear forces,” meaning that Russia has greater numbers and greater variety of what are sometimes called “battlefield nukes.” Furthermore, there may be relatively few Russian targets for U.S. tactical nuclear weapons that are both in theater and outside the Russian homeland. Finally, Russia could probably match any U.S. ability to defend against attacks at the level of limited homeland strikes. This is due in part to its willingness to field nuclear-tipped interceptors, whereas the United States relies upon the more challenging approach of directly striking incoming warheads in flight. Consistent with this finding, the Nuclear Posture Review describes a strategy of convincing Moscow that it “has no advantages in will, non-nuclear capabilities, or nuclear escalation options that enable it to anticipate a possible benefit from non-nuclear aggression or limited nuclear escalation.” This language is about denying Russia confidence in its ability to prevail, as opposed to defeating it outright, in unrestrained conflict.

Similarly, the strategy for China is to “prevent Beijing from mistakenly concluding that it could secure an advantage through the limited use of its theater nuclear capabilities.” Escalation dominance against China might be tempting but is not viable over the long term. The United States cannot expect to dominate at the large-scale strategic level because China’s ongoing nuclear modernization program is intently focused on ensuring its ability to operate there effectively. If the United States shifts to a more aggressive approach that seeks to negate Chinese strategic forces, China has the economic capacity to easily outpace these efforts and maintain the strategic objectives of its current program.

When it comes to countering Russia and China, even the less demanding strategy of flexible response sometimes requires adjusting U.S. nuclear capabilities. To help “prevent adversaries from perceiving advantage in limited nuclear escalation,” the Nuclear Posture Review directs lowering the yield of a small number of U.S. ballistic missiles, and potentially restoring a sea-launched cruise missile capability. These supplements do not offer dominance over the most capable opponents, but they do help ensure that future air defenses cannot negate U.S. flexibility to respond at lower levels of escalation.

Though not feasible for countering major nuclear powers, escalation dominance is a viable U.S. strategy against North Korea. The Nuclear Posture Review emphasizes “defensive and offensive capabilities to intercept and otherwise defeat North Korea’s missile capabilities, and thereby limit or preclude North Korea’s ability to conduct effective missile strikes[.]” That is, the United States will protect against and defeat North Korea even at the upper end of that country’s escalation ladder. Furthermore, U.S. policy is to “improve these capabilities as needed to stay ahead of North Korean missile threats” into the indefinite future. This is not a trivial determination, since North Korea’s ballistic missile capabilities have rapidly advanced over the last few years, and some argue that effective defense against even limited ballistic missile attack cannot be maintained or is already well out of reach. However, even imperfect U.S. defenses against ballistic missile attack constitute a meaningful advantage over a country with a limited long-range missile force, no such defenses of its own, and without the economic potential to compete over the long term.

Pursuing escalation dominance only against minor nuclear powers addresses most of the challenges Fitzsimmons identified. Flexible response remains the strategy of choice in cases where the conventional force balance might be narrowing. Escalation dominance can indeed drive arms-race dynamics, but the lesson is to never pursue it without the economic potential and the will to successfully race if necessary. Limiting dominance to countering states with markedly inferior military capabilities also diminishes the challenge posed by new and emerging technologies.

The Nuclear Posture Review’s tiered approach to escalation control strategy is sound, but was not a forgone conclusion. Views on how best to counter North Korea range from treating it like Russia and accepting the vulnerability of mutually assured destruction, to treating it like Iraq and undertaking preventive war. Some argue for pursuing full-spectrum military dominance over China and Russia, possibly extending up to defense against their ballistic missile forces. The Nuclear Posture Review took a measured position that is well-founded, but did not resolve these arguments. Furthermore, the security environment could change in ways that make the current approach untenable.

Over the Next Horizon

The tiered approach to escalation control strategy depends upon a clearly discernible difference between major and minor nuclear powers. Whenever an adversary approaches the point of transitioning from minor to major status, it is likely to strain the framework. For example, China’s conventional military advancement and its emerging nuclear second strike capability have placed it into the flexible response category of U.S. strategy, but the United States remains reluctant to explicitly acknowledge that it is vulnerable to China at the top of the escalation ladder.

It is North Korea, though, that poses the nearest-term real challenge. If North Korea continues to grow its nuclear forces, then at some point the capability suite the United States must field to stay ahead will look like an attempt to also dominate China.

This challenge is exacerbated when dominance over North Korea depends on offensive and defensive capabilities — such as the Ground-Based Interceptors currently at the core of America’s limited homeland ballistic missile defense system — that might also work against China and Russia. Maintaining a distinction between moves aimed at major and minor powers then depends on limiting the scale of U.S. deployments so that they can only threaten the smaller arsenals of minor nuclear powers, and on the ability of major powers to field more effective countermeasures on their offensive missiles. One potential way to keep ahead of the North Korean threat without upsetting the balance with China and Russia is to develop shorter-range boost-phase missile defenses that can cover North Korea but cannot reach into the interior of Russia or China. The United States could then deploy these to the region in lieu of continuing to increase the number of increasingly sophisticated interceptors.

If no such U.S. capability emerges and the North Korea nuclear problem remains unresolved over the next decade or so, the United States will have to either drop its strategy of dominance over North Korea or expect China to expand its nuclear capabilities even beyond current plans.

In any case, as long as adversaries possess the means of escalation, the United States must strive both to deter aggression and to avoid the worst outcomes in conflict. Escalation dominance is a good approach when it is achievable, but its feasibility is highly constrained by the relative capabilities among adversaries as well as their individual ones. In the next chapter of American nuclear strategy, the key challenge will be to respect those limits as the security environment continues to evolve.

Dr. Aaron Miles is a Fellow at the Center for Global Security Research at Lawrence Livermore National Laboratory. He served previously as Assistant Director for Nuclear and Strategic Technologies at the White House Office of Science and Technology Policy, and as a Senior Policy Advisor on Nuclear Deterrence in the Office of the Secretary of Defense. His policy interests include nuclear strategy, strategic stability, and arms control.

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

Image: International Campaign to Abolish Nuclear Weapons/Flickr