Deterring North Korea

January 29, 2021
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Can North Korea, and Kim Jong Un in particular, be deterred? The country has tested nuclear explosive devices six times since 2006. It currently possess a nuclear arsenal of approximately 60 warheads, potentially deliverable on a variety of platforms, including intercontinental, intermediate, medium, and short range ballistic missiles, and at least one submarine-launched platform. Since January 2019, North Korea has conducted at least 16 missile and rocket tests, most of which were short- or medium-range platforms.

Now that it is clear that nonproliferation efforts have failed, should the United States accept a deterrence relationship with North Korea? How urgent is the “complete, verifiable, and irreversible denuclearization of the Korean peninsula”? In order to answer these questions, policymakers must have a fundamental understanding of the principles underpinning deterrence. For more than two decades, the United States has begrudgingly come to terms with the need for a deterrence strategy against a nuclear North Korea, but it is clearly eager to not need one. Accepting a nuclear North Korea, even temporarily, seems like a nonstarter based on the United States’ unwavering demand for rapid and immediate denuclearization. The Biden administration, however, may have no choice but to embrace a deterrent relationship while pursuing other policy goals, which, importantly, should include the eventual denuclearization of North Korea.



North Korea is now a nuclear state presenting significant challenges to U.S. interests and security, as well as to the international nonproliferation regime. But all is not lost. Now that the weapons exist, it is most important to ensure that they are never used. In order to do this, the U.S. should consider embracing and enhancing deterrence while simultaneously approaching denuclearization in a firm but more patient approach. This should include halting or freezing further developments and offering sanctions relief and other incentives without demanding immediate complete denuclearization.

Principles of Deterrence

Ever since the atomic bombings of Japan in 1945, the unique characteristics of nuclear weapons, particularly the incredible scale of destruction and the speed with which it could be accomplished, led scholars and strategists to believe that these were weapons that couldn’t or shouldn’t be used in the traditional sense. As Bernard Brodie wrote in 1946, “the atomic bomb seems so far to overshadow any military invention of the past as to render comparisons ridiculous.” Instead, he argued, nuclear weapons made it so that the ultimate purpose of military forces would be to deter war rather than fight it. As a result, deterrence became the stated purpose of nuclear arsenals. Deterrence is an old concept, but a nuclear world required new theories about nuclear deterrence. Scholars and strategists were confronted with important questions. What exactly were the fundamental principles of nuclear deterrence? Upon which characteristics did a deterrent strategy now depend?

First, nuclear deterrence partially hinges on the principle that adversaries are (and perceive themselves to be) vulnerable to a threatened punishment. As Brodie stressed, vulnerability was a key component of deterrence, and it was deemed necessary to “explore all conceivable situations where the aggressor’s fear of retaliation will be at a minimum and to seek to eliminate them.”

Vulnerability is an important dimension of stable deterrence relationships for several reasons. First, it will make states more cautious, and states will refrain from even lesser provocations because of the fear of escalation and because the gains can be only limited, according to Kenneth Waltz. Second, as Waltz also highlights, a nuclear deterrent strategy “makes it unnecessary for a country to fight for the sake of increasing its security, and thus removes a major cause of war.” Third, specific to the case of nuclear dyads (i.e., when one nuclear-armed state faces off against another nuclear-armed state), strategic stability actually requires that both states perceive themselves to be mutually vulnerable.

In Arms and Influence, Thomas Schelling highlights that there must be significant concern about the vulnerability of the weapons themselves, not just the populations and cities of the adversary. He argues for measures available to both sides that would spoil the possibilities for surprise attacks. This might “stabilize deterrence and make it more reliable, assuring each side against being attacked and thus reducing each side’s incentive to attack.” An important implication of this argument is that if only one side were to make itself invulnerable to an attack, significant instability may result. For example, if the U.S. possesses perfect missile defenses or a completely effective counter-force capability (both of which North Korea may believe the U.S. to be attempting to achieve), Kim might believe there is nothing stopping the U.S. from attacking. In anticipation of this situation, there may be pressure on Kim to take aggressive action to avoid it. Fully effective defenses and counter-force postures, therefore, may contribute significantly to instability.

Related to but distinct from the principle of vulnerability is the principle of uncertainty. Uncertainty has two elements in terms of deterrence. First is the idea that though the adversary knows of the existence and scale of the nuclear state’s weapons, it cannot know the exact extent or location of nuclear capabilities. As Brodie argued, “The threat of retaliation does not have to be 100 percent certain; it is sufficient if there is a good chance of it, or if there is a belief that there is a good chance of it.” The second important element is uncertainty about the ability to control escalation and the risk that even limited conflict could inadvertently lead to nuclear war. For Schelling, the very essence of a crisis is its unpredictability and the fact that the participants are operating in a realm of risk and uncertainty. For him, “deterrence must be understood in relation to this uncertainty.” Moreover, uncertainty in crisis escalation implies that although states may have trouble credibly threatening a nuclear war, they will have equal difficulty promising that a nuclear war will not occur. Once a crisis starts, there is no guarantee that either state can control developments that follow — uncertainty that should encourage states to avoid crises and conflicts in the first place.

Robert Jervis expounds on the role of uncertainty, arguing that uncertainty is what makes nuclear weapons effective for deterring even limited wars, not just major attacks. “Because escalation can occur although no one wants it to, mutual second-strike capability does not make the world safe for major provocations and limited wars.” This logic contradicts arguments about a potential “stability-instability” paradox in which nuclear stability creates instability by making lower levels of violence safe. As Jervis argues, it is because we do not live in a “world of certainties – one in which decision-makers can predict how the other side will react,” that even limited conflicts are deterred. With regard to North Korea, this type of reasoning would imply that North Korea should refrain from initiating crises knowing that a larger and more dangerous conflict it cannot expect to win may result. Instead, North Korea will likely remain content with increased security, international recognition, and prestige .

Last, deterrence hinges on the assumption that the adversary is a rational actor. In its simplest sense, rationality denotes that actors can identify and rank their own preferences and can judge for themselves the best and likeliest way to achieve their goals. High risk-acceptance and eccentric or brutal behavior does not imply irrationality. Rational actors may be either risk-averse, or, as Kim appears to be, quite risk-acceptant. Rationality does not require that an actor’s preferences or perceptions should be the same as other actors. In addition, it doesn’t require that perceptions be accurate. Aggressive or risky behavior, therefore, is possible among rational actors depending on their goals, perceptions of available courses of action, and their associated assessed probabilities.

Do These Principles Apply to North Korea?

 With these principles in mind, can deterrence continue to work vis-a-vis North Korea? In short, yes. Throughout the evolution of the U.S-North Korean deterrence relationship, vulnerability has played an important role in the nuclear strategies and policies of both sides. The vulnerability of U.S. allies and assets in the region to North Korea’s intermediate-range missile and artillery barrages has almost certainly been a check on a more aggressive U.S. strategy, whether geared toward nonproliferation or regime change. It is certainly plausible that in the absence of this vulnerability the chances of the U.S. preventively attacking North during the Trump administration would have been higher, especially considering the extremely hawkish views of his national security adviser in 2017. As a result of this vulnerability, the U.S. routinely demonstrates its dedication to security agreements with allies in word and deed. Strategic bomber flights and military exercises, for example, demonstrate to North Korea their own vulnerability to U.S. and allied power in the region. Conversely, although the Kim regime would like nothing more than to unify the Korean Peninsula under North Korean leadership (dubbed the “holy grail of North Korean statecraft” in a recent report), it has refrained from overt and aggressive military action in pursuit of this goal. There is no doubt that Kim, like his predecessors, is wary of such behavior in the face of U.S. and allied military capabilities. Today, North Korea remains vulnerable to U.S. nuclear attacks, while the United States and its regional partners remain vulnerable to nuclear attack or retaliation from North Korea. This mutual vulnerability necessitates caution on both sides.

Recent progress in North Korean missile technology have made portions of the U.S. mainland vulnerable, giving the U.S. further reason to avoid unnecessary provocation. In 2017, North Korea conducted several tests of intercontinental ballistic missiles, two of which demonstrated the capability to potentially reach the continental United States. More recently, North Korea has successfully tested a submarine-launched ballistic missile  and has showcased a new and larger submarine-launched ballistic missile at a recent parade. As a result, the United States continues to invest significantly in homeland missile defense, as well as to deploy missile defenses to defend allies and assets in the region. Missile defenses likely contribute to increased feelings of vulnerability among Kim’s regime, which may see the build-up as a prelude to a military offensive. Though imperfect, these attempts to reduce vulnerability enhance deterrence by potentially denying North Korea the expected military gains from a limited missile attack, even as fully effective missile defenses might contribute to strategic instability. Regardless of their effectiveness, Kim will have to factor in these defensive capabilities when assessing the success of engaging in conflict and will question the ability to achieve even limited goals through limited means. For example, in order to ensure the success of a missile attack, Kim would have to increase the size of the salvo in order to compensate for missiles likely to be shot down by U.S. and allied defenses. But knowing that a larger initial attack would be perceived as particularly aggressive and would likely invite a larger counter-attack, he might be deterred from pursuing whatever limited gains a smaller attack might have achieved. From Kim’s perspective, U.S. military capabilities are more than sufficient to make military success for North Korea in any conflict appear difficult and costly. Vulnerability to severe retaliation and punishment from U.S. strategic forces is also currently unavoidable for Kim. In fact, this very vulnerability has driven the North Korean nuclear program toward a capability to directly threaten the U.S., thereby demonstrating its own acknowledgement of vulnerability. In sum, both sides are vulnerable to each other. Most importantly for U.S. decision-makers, there is no likely development in the near to medium term that might remove this sense of vulnerability from Kim’s mind.

There is also great uncertainty in the nuclear capabilities and red lines of each side, in particular concerns about what might cause Kim to feel existentially threatened, and concerns over what might trigger the United States to exercise nuclear defense on behalf of its allies in the region. Kim consistently expresses concerns about regime survival and fear of a U.S. attack, and recent U.S. regime change operations in other states only strengthen this fear. While the United States should be careful not to inadvertently increase this threat level to a point where Kim believes he must start a major war, the threat of nuclear retaliation should be maintained. Such a scenario is far from implausible (nuclear scholar Jeffrey Lewis sketches out a hypothetical nuclear war between North Korea and the United States in a recent novel). Missile defenses also add an important element of uncertainty to the relationship. Uncertainty about the effectiveness of these systems should induce caution on both sides because neither can be completely sure about how effective the systems will be (though these systems may also strengthen resolve on the part of the U.S. if deemed very effective, as Robert Powell suggests). Although the United States has been clear in its statements regarding North Korean nuclear use, for example stating in the 2018 Nuclear Posture Review that “there is no scenario in which the Kim regime could employ nuclear weapons and survive,” uncertainty remains about which actions beneath the nuclear threshold might trigger a larger response. This uncertainty will undoubtedly induce caution in even lower-level conflict behavior. The U.S. explicitly includes some level of ambiguity and uncertainty in its declaratory statements, such as when describing possible conditions for nuclear use, saying, “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.” This type of statement leaves plenty of room for adversaries to question what might trigger a response and makes any aggression against the U.S. or its allies a risky proposition.

Last, both Kim and leaders in the United States and its allies appear to remain rational actors despite recent bombastic behavior and inflammatory rhetoric (which may be plausibly attributed to clumsy signaling attempts). Kim may be a cold and brutal oppressor, but his behavior should be seen as quite rational if you make the very supportable assumption that, like most political leaders, his primary goal is keeping his regime alive and keeping himself in power. As others have noted, “Kim is a tyrant, but I don’t think he is suicidal.” Kim continues to build and enhance his nuclear weapons capability in reaction to real and proximate threats to his very survival. The United States frequently conducts exercises with South Korea and Japan, and North Korea frequently decries these exercises as hostile and reckless. Kim sees these exercises as practice events for an eventual attack on North Korea. The United States has also stationed missile defense capabilities in South Korea and Japan, as well as on ships in the region. Kim’s continued pursuit of enhanced nuclear capabilities in response is as rational as it is for the U.S. to want to mitigate its own vulnerability. Frequent military deployments to the region, and overflights of U.S. strategic (nuclear capable) bombers also serve to enhance the perception of threat on behalf of Kim. These security dilemma dynamics have certainly contributed to Kim’s rational pursuit of an enhanced nuclear weapons capability. On top of these very visible military measures, recent dramatic increases in hostile rhetoric from former President Donald Trump, such as his “fire and fury” remarks, have only served to solidify Kim’s perceived need for a nuclear deterrent to potential U.S.-backed regime change. Of course, deterrence requires clear communication and credibility, which includes demonstrating capability. Kim is well aware that if he were to engage in any sort of large scale aggressive military behavior against his neighbors, this could spell the end of his regime. He also has no reason to doubt the U.S. capability and opportunity to respond to threats from North Korea. Assuming, as I do above, that Kim desires to remain the leader of his country and to preserve his regime, he has little incentive to test the U.S. nuclear deterrent. Whether his eccentric and brutal behavior leads to some other inadvertent escalation is a different question. As far as U.S. leaders are concerned, assuming Kim is rational enough to know what he wants and to recognize how he can lose it seems to be a safe bet.

Implications for U.S. Policy

North Korea will require careful attention from the Biden administration, and the United States and other powers will need to continue to carefully craft a deterrence strategy to deal with Kim. As the commander of U.S. Strategic Command recently said, specific adversaries require tailored deterrence strategies. All of these potential strategies, however, are underpinned by the time-tested principles of deterrence listed above. Deterrence will work with North Korea so long as both sides avoid provocative steps to undermine strategic stability. The goal of a nuclear-free Korean peninsula should remain an unwavering aspiration and nonproliferation efforts are an essential part of that goal. Understanding that deterrence is still operative, however, may help to avoid inadvertent or unnecessary conflicts that result from fear that certain leaders or countries are categorically undeterrable, or that denuclearization must happen immediately.

Policymakers should avoid an undue sense of urgency to immediately denuclearize North Korea, which may precipitate unwanted conflict and make it harder to secure less ambitious concessions from North Korea (e.g., a moratorium on testing intercontinental ballistic missiles and nuclear tests). Since deterrence can and does work, “bringing the hammer down” in order to achieve the maximalist goal of denuclearization immediately may be unnecessary and dangerous. Officials should consider the establishment of a stable deterrence relationship under which confidence-building and cooperative measures may be undertaken to pursue the ultimate goal of denuclearization through shorter-term goals such as halting further weapons development and preventing horizontal proliferation. This is in line with other recent arguments noting that though political compromise is risky, it is almost certainly necessary to make progress on denuclearization. Maintaining a robust deterrent strategy is a major source of risk management and is exactly what may allow the Biden administration to accept some of this risk. Others who argue for compromise, such as a “big, bold, conciliatory” approach, implicitly or explicitly rely on deterrence stability as the insurance policy for taking on the risk. My argument, therefore, supports their recommendations to be willing to make concessions and play the long game when it comes to denuclearizing North Korea. It is not, however, an argument to allow the North Korean program to continue to grow unchecked. Rather, it is an argument that deterrence may operate to reduce the risk of a more patient approach.

A second implication is that if the U.S. embraces a deterrence relationship with Kim and North Korea it will need to consider new modes of communication and cooperation, similar to measures like “hot lines” taken with other adversaries like Russia and China. Stable deterrence requires minimizing the chances of misperception and accidents. In order to truly establish stable deterrence, measures like this will be necessary and may also have the upshot of broadening the venues available for peaceful and cooperative communication between the countries.

In the near term, a nonnuclear North Korea is less important than avoiding a nuclear war. The nonuse of nuclear weapons is just as critical as the nonpossession of them. Deterring their use is possible while at the same time working, in a firm but new and more conciliatory way, toward their eventual removal.



Cmdr. Daniel Post, U.S. Navy, is a Ph.D. candidate studying international relations at Brown University. His research centers on nuclear deterrence strategy, policy, and the role of nuclear weapons in international relations, with a focus on the concept of limited nuclear war. He is currently serving in his 20th year of active duty naval service and is assigned to the Permanent Military Professor Program at the U.S. Naval War College in Newport, Rhode Island. 

The views expressed in this essay are the author’s alone and do not reflect or endorse the views of the U.S. government, the Department of Defense, or the U.S. Navy.

Image: Defense Department (Photo by D. Myles Cullen)