U.S. security guarantees are extraordinary and complex commitments. The United States puts at risk its deployed forces and personnel, and potentially its homeland, for the sake of shared interests with allies. While the benefits of each alliance are unique, they provide the United States with security and economic partners that help to maintain international stability, promote economic growth and trade, and protect liberal values. But in extending deterrence to cover allies, the United States also increases its likelihood of being drawn into an unwanted war. As a result, the United States must sometimes deter its allies from undertaking certain actions and, conversely, assure its adversaries that it will behave in a measured manner. Plainly, it must balance assurance and deterrence both among and between its allies and potential adversaries.

To help inform U.S. policy choices, this article unpacks U.S. deterrence and assurance challenges. It begins with a discussion of U.S. extended deterrence of adversaries and assurance of allies along with an introduction of a Pacific Forum CSIS table-top exercise involving a Korean peninsula scenario. Then, drawing on the exercise and other historical examples, it shows why and how, somewhat counter intuitively, the United States deters allies and assures adversaries. In the third section, the article examines U.S. deterrence and assurance of both its allies and adversaries in the current security environment, highlighting the inherent problems that this creates among allies, among adversaries, and between allies and adversaries.

Deterring Adversaries and Assuring Allies

The United States maintains a network of alliances around the globe, each with unique characteristics. Yet central to each alliance is a robust military relationship and a commitment to mutual defense, with the United States as the more powerful state taking on a greater share of the defense burden. Washington honors its security guarantees to allies by committing its nuclear and conventional forces to deterring adversaries from attacking its allies and assuring allies that the United States will defend them if they are attacked. U.S. extended deterrence relies on a combination of capability and will. But most important, the effectiveness of extended deterrence and assurance depend on the perception of adversaries and allies respectively.

The fundamentals of extended deterrence and assurance were demonstrated at a track-1.5 table-top exercise that the Pacific Forum CSIS ran in Maui, Hawaii in July 2014. The exercise featured teams of U.S., Japanese and South Korean nationals from academia, think tanks, government and the military managing an escalating crisis on the Korean Peninsula. It began with the sinking of a Japanese vessel by North Korea in the Sea of Japan/East Sea, leading all three teams to recommend that the United States, with logistical support from Japan, strike the North Korean naval base that supported the attack. The U.S. team acted out of concern for Japan’s security, the credibility of the U.S.-Japan alliance and, by extension, the credibility of the entire U.S. alliance system. In the second move, North Korea retaliated with an artillery barrage against South Korean farmland north of Seoul (killing several people) and a nuclear detonation over the Sea of Japan/East Sea (with no initial casualties). While the U.S., Japanese and South Korean teams disagreed over how to respond, many felt that the United States needed to put an end to North Korea’s active nuclear weapons and long-range missiles. The U.S. team, in line with the 2014 U.S. Quadrennial Defense Review, felt it could not allow Pyongyang to “escalate [its] way out of failed conventional aggression.” It was also motivated by a desire to hold North Korea accountable for breaking the nuclear taboo and to send a message to other states that future nuclear use would have severe consequences.

The responses of the U.S., Japanese and Korean teams were somewhat predictable and in line with common understandings of extended deterrence and assurance. But the Maui exercise also exemplified that, at times, the United States seeks to discourage, or deter, actions by its allies and, conversely, assure its adversaries. U.S. efforts to deter allies and assure adversaries should not be surprising. Deterrence—the act of using fear of consequences or punishment to change a country’s calculus and inhibit behavior—has been a key feature of alliance relationships, just as assurance—the act of using declarations or guarantees to inspire confidence in how a country will act in particular circumstances—has been central to adversary relationships. But in the twenty-first century, more so than during the Cold War, the United States faces increasingly complex challenges in managing its alliance and adversary relationships.

Deterrence in Alliance Relationships

Elements of deterrence have long been discussed as a key component of alliance relationships. In his study of alliances during the 1815-1945 period, Paul Schroeder concludes that alliances are not only “weapons of power,” but also “tools of management” or, as he puts it, “pactum de contrahendo” (pacts of restraint). But the deterrence factor in alliance relationships was perhaps best captured by nineteenth-century Prussian statesman Otto von Bismarck who, after allying his country with Austria to stop Vienna’s provocative policies toward Russia and prevent a major war, famously remarked that in every alliance “there is always a horse and a rider.”

The fundamentals of the current U.S. alliance system are no different. As Victor Cha explains, the United States established tight and deep bilateral alliances with Taiwan, South Korea and Japan after World War Two both to contain the Soviet threat and to exercise control over, as he puts it, potentially “rogue allies” that could entrap the United States in unwanted wars. Washington set up processes that allowed it to persuade allies of the need for caution and mechanisms for joint decisions that constrained their options. Perhaps more important, there was an implicit, background threat: ‘if you escalate too far on your own, the United States may not support you.’ Because allies were militarily dependent on the United States, they were deterred from overreacting when crises arose and, for that matter, from initiating crises in the first place.

The Maui exercise exhibited the tension that sometimes exists between the United States and its allies. Following Pyongyang’s attack against South Korea, South Korean participants stressed that retaliation would likely be “automatic”—initiated by commanders in the field before consultation with Washington, and possibly even Seoul—and go beyond a proportionate response, striking “vital” North Korean targets. American participants, while fully recognizing South Korea’s right to respond unilaterally at the local conventional level, worried that such a military response would escalate the conflict. Some pointed to the 2013 U.S.-South Korea Counter-Provocation Plan, which includes procedures for consultation for a combined U.S.-South Korean response. Others noted that there may be a difference of interpretation between U.S. and South Korean officials about which North Korean targets should be included in a retaliatory strike. In short, the U.S. team wished to maintain control over South Korea and was prepared to restrain, constrain and possibly even deter, some of Seoul’s actions.

Similar dynamics have been at play in Europe. In 1949, Washington helped to establish the North Atlantic Treaty Organization (NATO) to deter a Soviet invasion of Europe, but also to control allies and, in particular, prevent Germany from remilitarizing and developing nuclear weapons. The famous statement reportedly made by Hastings Ismay, NATO’s first secretary-general, that the purpose of the alliance is “to keep the Russians out, the Americans in, and the Germans down” is revealing.

Of course, even when Washington deters its allies, it does so in different ways than it deters its adversaries. In dealing with the latter, the United States deters large-scale conventional war or nuclear use by threatening military retaliation. With allies, the United States does not threaten military action, but it has, on more than a few occasions, used threats to change their calculus. In response to South Korea’s decision to pursue nuclear weapons in the 1970s, for instance, U.S. diplomats told their South Korean counterparts that Washington would “review the entire spectrum of its relations with [Seoul], including security and economic arrangements.” Seoul reacted by pausing its program, before restarting it in the 1980s. The Ronald Reagan administration responded by offering a stronger U.S. security guarantee, while explaining to Seoul that rejecting the offer would lead to sanctions and a withdrawal of U.S. security and economic aid. South Korea agreed to give up its nuclear-weapon program—it was deterred by the threat of abandonment.

Assurance in Adversary Relationships

Like deterrence in alliance politics, states have long offered assurances to adversaries. For an important period before modern-day warfare, there was tacit understanding—a form of assurance—among adversaries that military engagement would spare civilian populations, thereby limiting the scope of war. Even as the differentiation between combatants and non-combatants diminished as a result of significant advances in technology, the advent of mass conscription, and rising nationalism from the late nineteenth century onward, adversaries continued to assure each other. The continued evolution of warfare and international relations prompted the codification of several previously customary assurances regarding jus ad bellum (the law of war, or to engage in war) and jus in bello (the laws during war, or humanitarian law) and the establishment of the League of Nations in 1920 and then the United Nations in 1945.

Following the nuclear revolution, the requirements for assurances among adversaries increased. When the United States and the Soviet Union realized after the Berlin and Cuban missile crises of the early 1960s that they had the power to destroy the planet, they devoted considerable time and energy to stabilizing their relationship. The operating model became nuclear deterrence, or the threat of massive destruction in retaliation for an act against one’s vital interests.

Nuclear deterrence required the two superpowers to simultaneously threaten and assure each other. As Thomas Schelling puts it, “the threat of massive destruction may deter an enemy only if there is a corresponding implicit promise of non-destruction in the event he complies.” Talking specifically about the role of assurance as an essential component of deterrence strategy, Schelling argues that, “To say, ‘One more step and I shoot,’ can be a deterrent threat only if accompanied by the implicit assurance, ‘And if you stop I won’t.’” Nuclear deterrence strategy also led the United States and the Soviet Union to maintain effective and survivable second-strike capabilities and, as a general rule, to assure each other that they would remain mutually vulnerable to nuclear retaliation. These assurances crystallized in various arms-control agreements and confidence-building measures, which regulated U.S. and Soviet nuclear capabilities and intentions and helped maintain a stable balance of terror, however imperfect it may have been, until the end of the Cold War.

The Maui exercise demonstrated the need for assurance of adversaries during a crisis. Each team attempted to provide “off-ramps”—de-escalatory options—to North Korea throughout the exercise. The U.S.-Japan response to North Korea’s initial aggression was decisive but proportional, suggesting that it was intended to be retaliatory, not escalatory. More important, while the U.S. team refused to let Pyongyang use nuclear weapons to terminate the conflict and recommended action to destroy North Korea’s nuclear arsenal, it stopped short of recommending regime change. Some even suggested a more limited strike that would hit key military targets without attempting to eradicate North Korea’s nuclear retaliatory capability. While fully recognizing the difficulty of signaling America’s limited intentions, participants tried to calibrate their response to assure Pyongyang that its survival would be guaranteed if it chose not to retaliate. This is consistent with U.S. Strategic Command’s Deterrence Operations Joint Operating Concept, which stresses the importance of considering the adversary’s “perception of the consequences of restraint or inaction”—that is, giving North Korea an exit to the crisis that Pyongyang can accept.

While assurance is common in adversary relationships, it is nevertheless different from assurance in alliance relationships. In both cases, the United States seeks to assure other countries that they can be confident about how the United States will act in particular circumstances. Yet, with allies, the United States often provides positive guarantees—promises to do something to address a problem—whereas adversaries are generally provided negative guarantees—commitments not to do something threatening.

Deterring and Assuring Allies and Adversaries in the Twenty-First Century

The United States continues to assure its adversaries even as it deters them, just as it deters its allies even as it assures them. In the current security environment, however, this task is more challenging because Washington adopts different approaches for different allies and adversaries.

Allies

In recent years, Washington has ramped up assurance of allies, mostly at their request. In Europe, this occurred in the context of NATO’s latest revision of its “Strategic Concept” in 2010 and its Deterrence and Defense Posture Review in 2012. In Northeast Asia, Washington used newly-established bilateral extended deterrence dialogues to assure Japan and South Korea.

But Washington has also sought to ensure appropriate burden sharing by encouraging its allies to better defend themselves. President Richard Nixon’s 1969 “Guam Doctrine,” for instance, emphasized that the United States “shall look to the nation directly threatened to assume the primary responsibility of providing the manpower for its defense.” Today, officials in Washington continue to believe that allies need to do more. There is an enduring disdain for free-riding and a growing realization that, in the current fiscally-constrained environment, the United States needs allies to more actively contribute to strengthening regional security architectures. The United States is, for example, working with Japan to strengthen its regional missile defense architecture by co-developing the Standard Missile-3 (SM-3) Block 2A interceptor. Seeing an opportunity for Japan to contribute even more, several Americans in Maui recommended that Japan develop its own long-range strike capability to respond to Korean Peninsula contingencies. They stressed that such capability would be particularly useful because the United States, under the terms of the U.S.-Russia Treaty on Intermediate-Range Nuclear Forces (INF Treaty), cannot legally deploy intermediate-range land-based missiles.

Yet while the United States encourages Japan—and its allies generally—to do more, it also seeks to maintain control. After recommending that Japan develop its own strike capability, the U.S. team cautioned that Japan should only use such a capability for coordinated actions within the framework of the U.S.-Japan alliance. While they wanted to encourage Tokyo to play a greater role in its own defense, Americans were equally eager to prevent Japanese actions that would increase the risk of U.S. entrapment. This frustrated Japanese participants, leading one to state that “sometimes it looks like you’re setting [Japan] up for failure, asking [Tokyo] to do more but not too much.”

The challenge for Washington is to properly manage expectations while avoiding mixed messages. The bilateral extended-deterrence dialogues established with Japan and South Korea in 2010 have made great strides in bringing Washington closer in sync with its Northeast Asian allies, but uncertainties remain. Managing expectations of allies is especially difficult because, in the current complex security environment, the United States has different expectations for different allies and regions. Allies do not fully understand why Washington expects actions by some that it denies to others.

U.S. expectations of European and Northeast Asian allies about extended nuclear deterrence, for example, differ considerably. In Europe, while the “supreme guarantee” of the security of NATO allies is provided by U.S., UK and French nuclear forces, the United States also forward-deploys nuclear weapons that it operates on dual-capable aircraft with its NATO allies. Moreover, the alliance’s nuclear roles and responsibilities are coordinated by the defense ministers of all member states, except France, in the Nuclear Planning Group. No such sharing arrangements exist in Northeast Asia, where extended nuclear deterrence is guaranteed by the U.S. nuclear triad of strategic delivery systems and the U.S. capability to forward-deploy nuclear weapons on bombers and fighter-bombers, should this become necessary. In other words, the Northeast Asian extended nuclear deterrence model relies solely on reach-back capabilities rather than forward-deployed systems.

Yet, as the Northeast Asian security environment deteriorates—with continued North Korean nuclear threats and increased Chinese assertiveness—experts in Japan and South Korea more frequently debate whether the U.S. nuclear umbrella in Asia should evolve toward an arrangement that more closely resembles the NATO model. At the official level, South Korea and Japan, at least thus far, simply want to better understand the NATO model and improve the respective bilateral extended-deterrence dialogues. But some influential people in South Korea, and to a far lesser extent Japan, have gone as far as calling for the development of independent nuclear weapons.

Washington also rejects the development of indigenous nuclear weapons by its allies. The Nuclear Posture Review Report makes clear that U.S. alliances, among other things, serve nonproliferation goals by acting as guarantees to non-nuclear allies that “their security interests can be protected without their own nuclear deterrent capabilities.” Implicit in this statement is that development of nuclear weapons by a U.S. ally would be a step too far and eliminate one of the important side benefits the alliance provides. The deterrence message is obvious: ‘develop nuclear weapons and you may be on your own.’

Proponents of nuclear weapons in South Korea and Japan note the tension in U.S. policy. While Washington currently forward-deploys nuclear weapons in Europe, it solely maintains the capability to do so in Asia, and this difference is likely to persist. In the wake of Russia’s intervention in Ukraine, even advocates of the withdrawal of U.S. nuclear weapons from Europe admit that it is unlikely to happen anytime soon. Rather, Nikolai Sokov and Miles Pomper suggest that “the debate will evolve in the opposite direction: some members of the alliance will insist on increasing reliance on nuclear weapons, while others will defend the status quo.” This debate, in fact, has already begun, with influential U.S. figures making a vigorous case against withdrawal and Polish anti-communist icon Lech Walesa arguing that Poland should “lease nuclear weapons” to ward off Russia.

Another important difference is that the United States works in tandem with two nuclear-armed states in Europe—the United Kingdom and France—to provide the supreme guarantee of NATO’s security, whereas it resists the development of nuclear weapons by its Asian allies. While the United Kingdom and France went nuclear before the conclusion of the Nuclear Nonproliferation Treaty (NPT), and thus did not violate international law, some in Seoul, Taipei and Tokyo may wonder if, when push comes to shove, the United States could accept a repeat of the European experience. Washington, however, continues to adamantly reject the development of nuclear weapons by any of its allies.

Adversaries

Like with its allies, the United States deters and assures its adversaries. Unlike during the Cold War, however, it adopts different approaches for different potential adversaries. Back then, Washington viewed almost everything through the lens of a monolithic Soviet threat. Today, facing a more diverse and independent set of potential adversaries, the United States tailors its approach to each, using both nuclear and non-nuclear tools. In particular, U.S. policy toward Russia and China differs considerably from its approach to North Korea, and this has important implications for both deterrence and assurance.

With Russia and China, states that are not strictly categorized as U.S. adversaries, Washington accepts mutual vulnerability—explicitly with Moscow and implicitly with Beijing—as the operating model for stable relations. It seeks to assure them that it will avoid developing and deploying capabilities that could negate their retaliatory nuclear forces, reducing the incentive for either the United States or its potential adversaries to deploy additional nuclear forces or use nuclear weapons first in a crisis for fear of a disarming first strike. With both states, the United States also seeks to improve strategic stability, building upon the many economic, political and security interests that they share, while steering clear of potential military flashpoints. With Russia, the only country with which it shares a similar-sized nuclear arsenal, the United States seeks to do so by advancing the existing bilateral arms-control process currently codified in formal agreements like the New Strategic Arms Reduction Treaty (New START) and the INF Treaty, while simultaneously pursuing broader strategic dialogue in forums such as the NATO-Russia Council. With China, the United States hopes to initiate a similar dialogue on strategic stability, which it has long requested, and, ultimately, to develop an arms-control relationship.

So far, however, there has been little progress. The prospects, in fact, are dim. Russia has invaded Ukraine, violated the INF Treaty, and maintained an important role for nuclear weapons in its military doctrine, clearly identifying the United States and other NATO members as its enemies and spelling out conditions under which it would launch a preemptive nuclear strike. Over the past several months, Moscow has also taken important steps to modernize its nuclear forces. Meanwhile, in addition to showing increasing assertiveness in the maritime domain, China continues to modernize and expand its nuclear arsenal and its conventional forces. While there has been successful track-1.5/2 dialogue between the United States and China, Beijing continues to resist official government dialogue on nuclear weapons and strategic capabilities, raising suspicions in Washington about its policies, thinking and intentions.

Unlike with Russia and China, the United States rejects mutual vulnerability as the basis of its strategic relationship with North Korea. It maintains the option of carrying out a disarming strike, or even going further and pursuing regime change. But, of course, having the option to disarm does not mean the United States will use it. In certain instances, Pyongyang may do something so deplorable or seemingly irrational that Washington would accept nothing less than regime change. In other scenarios, such as the one played out in Maui, the United States may instead opt to retaliate, deter and punish, but keep its aims limited and assure its adversary that it has a way of exiting the crisis.

Like with allies, the United States faces several challenges because it uses different approaches with different adversaries. In rejecting mutual vulnerability with North Korea, for instance, the United States maintains a missile defense architecture designed to counter the evolving ballistic-missile threat that Pyongyang poses to its homeland, the forces it deploys overseas, and its allies. As laid out in the Ballistic Missile Defense Review Report, Washington attempts to do so while assuring China and Russia that its deployments are “not intended to affect the strategic balance.” But as North Korea’s missile program improves, the United States continues to research technologies to stay ahead of the curve and deploy additional, more sophisticated interceptors. This complicates its task of assuring China and Russia that U.S. capabilities will not grow to the point that they do affect the strategic balance. Linton Brooks and Mira Rapp-Hooper describe this as a “security trilemma.”

As a result, the Shanghai Cooperation Organization, led by China and Russia, stressed in its latest declaration that “the unilateral and unlimited strengthening of missile defense systems by any individual state or any group of states will undermine international security and strategic stability.” China and Russia have also voiced objections to the deployment of Terminal High Altitude Area Defense (THAAD) batteries in South Korea. Washington, of course, regularly reminds both Beijing and Moscow that more efforts on their part to limit and rollback Pyongyang’s capabilities would help phase out this trilemma, but, for the most part, Russia and China have been unwilling to exert substantial pressure.

Allies and Adversaries

U.S. policy vis-à-vis its adversaries also has implications for its relationships with its allies, and vice versa. In 1984, Glenn Snyder explained that “the security dilemma occurs in relations between allies as well as between adversaries […] Choices in each dilemma are constrained not only by predicted or feared effects internal to itself, but also by side effects in the other dilemma. In particular, strategy choices in the adversary game—conciliation or firmness—are constrained by fears of abandonment or entrapment by allies.” Thirty years later, Snyder’s words continue to ring true.

Decisions that the United States makes to assure or deter its allies have consequences for its relationships with its adversaries. On one end of the spectrum, too much U.S. restraint or constraint of allies can reduce its ability to deter adversaries. For that reason, Washington has been, however cautiously, encouraging its allies in Northeast Asia and Europe to participate in collective efforts to strengthen regional security architectures through the development of effective missile defense, conventional strike capabilities, and integrated command and control systems.

At the other end of the spectrum, too much U.S. assurance of allies can also create serious problems. For example, believing that Taiwan had unconditional U.S. support, President Chen Shui-bian, whose Democratic Progressive Party ruled in Taiwan from 2000 to 2008, began to push for Taiwanese independence. Washington was quick to respond by clarifying its position, stressing that it would defend its ally against an unprovoked attack from China, but that it would not support unilateral moves toward independence. The United States thereby deterred Taipei from excessive action and assured Beijing that its “one China” policy had not changed. A similar dynamic played out in the fall of 1956 when Israel, followed by Britain and France, invaded Egypt to regain Western control of the Suez Canal. The three U.S. allies initially attained their military objectives, but wrongly assumed that they would receive U.S. support and were eventually forced to withdraw. Washington showed Tel Aviv, London and Paris that U.S. alliances do not give allies carte blanche to do anything they want and expect U.S. support.

By the same token, the decisions that the United States makes to deter or assure its adversaries have a direct impact on its allies. Too much U.S. deterrence of adversaries can make U.S. allies nervous. In a discussion of Western European defense during the Cold War, Michael Howard argues that “proposals to make nuclear war ‘fightable,’ let alone ‘winnable,’ by attempting to limit its targets and control its course, however much sense this may make in the military grammar of deterrence, are not persuasive in the political language of reassurance.”

On the other hand, too much U.S. assurance of adversaries can, by contrast, create fears of abandonment among U.S. allies. While Washington is committed to developing stable strategic relations with Beijing, many U.S. officials and experts feel that the United States cannot publicly accept mutual vulnerability with China, at least in part because of resistance from the Japanese, who believe that such an acknowledgement would signal weakness and embolden China to more assertively promote its interests at Japan’s expense. Many in Japan argue that U.S. acknowledgement of mutual vulnerability would decrease Japan’s security.

Conclusions and Recommendations

The United States constantly balances deterrence and assurance with both its allies and adversaries. With allies, the United States is primarily concerned with offering protection to maintain lasting partnerships that guard its regional and global interests, but it also seeks to prevent nuclear proliferation and to avoid being drawn into unwanted wars. With adversaries, the United States maintains a robust military posture to deter them from challenging U.S. interests or those of its allies, but it also signals the limits of U.S. intentions, offering them security in peacetime and off-ramps during crises. With both allies and adversaries, the United States must manage its messages because they are heard by multiple audiences at once. This is a difficult task because the United States uses different approaches with different allies and adversaries, sometimes creating issues and even tensions not only between allies and adversaries, but also among allies and among adversaries.

Washington, therefore, must weigh benefits, costs, and risks as it dances between assurance and deterrence of allies and adversaries, recognizing that it will often have to make less than optimal compromises. So far, the United States has done well in managing these challenges, but the task of aligning U.S. policy to the changing security environment is a constant work-in-progress.

To better balance its relationships with its allies and adversaries, Washington should begin by taking the following five steps.

First, it should avoid the need to deter or restrain allies by continuing to coordinate plans for military contingencies. Washington should pay particular attention to low-level provocations, where there is some ambiguity about appropriate roles and actions. It should give allies the freedom and confidence to respond independently to low-level provocations, but, just as important, clearly communicate to allies what they can expect from the United States and what is out of reach. In short, the United States should continue to deter with its allies, presenting a united front to adversaries.

Second, Washington should ensure that it has the ability to assure adversaries during a crisis by maintaining capabilities and plans that allow it to execute a diverse set of conventional and nuclear strike options. It should develop robust crisis-management mechanisms with nuclear-armed adversaries and ensure that it can convey limited intentions when appropriate. With respect to North Korea, Washington should establish decision criteria for when to carry out limited strikes, as opposed to attempting to disarm its nuclear capability or pursue regime change, and ensure that it has the ability to signal in a crisis by communicating during peacetime and taking advantage of intermediaries.

Third, Washington should ease the tension between its differing approaches to extended deterrence and assurance in Europe and Northeast Asia. To increase allies’ understanding of why deterrence models are different in the respective regions, Washington should facilitate cooperation between European and Asian allies to cross-pollinate ideas about how to better tailor deterrence. At the same time, Washington should ease the tension between its two regional deterrence models by emphasizing that U.S. central nuclear systems are the core pillar of extended deterrence in Europe, just like in Northeast Asia.

Fourth, Washington should be more realistic about the assurances that it can provide to adversaries during peacetime. As the North Korean nuclear and long-range missile programs advance, the United States is likely to deploy a larger and more capable missile defense architecture. At some point, this will make it difficult, if not impossible, to assure China that U.S. missile defense deployments do not affect the reliability of Beijing’s nuclear second-strike capability. Washington should recognize this and plan accordingly.

Finally, Washington should use its extended deterrence dialogues with Japan and South Korea to set the groundwork for future assurances of China. If Washington brings Tokyo and Seoul to understand that U.S. extended deterrence would remain effective even if it were to, for example, publicly acknowledge mutual vulnerability with China, then it would have greater flexibility to, if and when it deems it necessary, provide an assurance to China without causing allied anxiety.

David Santoro is a senior fellow for nuclear policy at the Pacific Forum CSIS in Honolulu, HI. John K. Warden is a strategic analyst at the Scitor Corporation, an SAIC company, in Arlington, VA. These opinions are those of the authors and do not represent those of their employers or clients.

Image: Flickr/Naval Surface Warriors.