From Punishment to Denial: Stabilizing Deterrence on the Korean Peninsula

Introduction

The time has arrived to recalibrate the paradigm of deterrence on the Korean Peninsula. Without prudent adjustments, the United States and South Korea — the Republic of Korea, or ROK — could sleepwalk into dangerous military escalation and nuclear war with North Korea. 

For more than a decade, the U.S.–ROK alliance has relied on the doctrine of “deterrence by punishment” in order to deter North Korean military aggression. The key element of deterrence by punishment is the threat of a severe, overwhelming military response.¹The logic behind this deterrence strategy is straightforward: to make the costs of aggression completely unacceptable to the aggressor.²

This strategy — at least on the surface — has been relatively successful. The Korean Peninsula has not witnessed an “immediate deterrence” crisis in years.³Nor, according to the consensus among experts, is North Korea likely to seek war given the vast military gap between itself and the United States and South Korea.⁴This apparently placid surface, however, is misleading; it masks growing risks that, if left unresolved, could lead to an increasingly fragile and unstable deterrence relationship for crises short of an invasion or a nuclear attack.⁵

As a strategy, deterrence by punishment is a hammer. But not every crisis is a nail. Deterrence by punishment has succeeded in deterring North Korea from the two ultimate acts of aggression that the U.S.–ROK alliance is intended to prevent: invasion and nuclear attack.⁶But the alliance does not have a diverse enough set of credible policy tools to employ in response to North Korean threats or provocations lower on the “ladder of escalation” — referred to in this brief as “gray zone” aggression.⁷The U.S.–ROK alliance is ill-positioned to proportionately retaliate against North Korean escalation or exercise restraint based on the actions and interests at stake in an immediate deterrence scenario. The credibility of deterrence by punishment for gray zone aggression is at risk of hollowing, increasing the potential for deterrence failure and military conflict.

This brief argues that the U.S.–ROK alliance would be better positioned to deter and respond to North Korean gray zone aggression by reorienting deterrence around the principle of “denial” — building defensive capabilities and bolstering the resilience of U.S.–ROK forces to “deny” or lower the effectiveness of North Korean attacks. The alliance would still rely on deterrence by punishment for deterring a North Korean invasion of South Korea or a North Korean nuclear attack. For all other scenarios below those thresholds, however, the U.S.–ROK alliance should shift its deterrence strategy to denial. Denial-oriented deterrence would allow the alliance to maintain robust wartime readiness while increasing its ability to successfully manage gray zone scenarios. The alliance would be in a better position to match North Korean escalation move for move or exercise restraint without jeopardizing its deterrence credibility. The proposed shift would also improve deterrence by serving to reduce North Korea’s existential fears in a military crisis and hence the danger of North Korean overreactions. 

Deterrence, however, is only a temporary solution. By itself, deterrence is insufficient to promote the underlying political shifts necessary for durable stability on the Korean Peninsula. This brief also argues that the U.S.–ROK alliance should vigorously pursue diplomacy and arms control negotiations with North Korea based on realistic goals and expectations, dropping in particular the demand for full denuclearization.

The state of deterrence on the Korean Peninsula

Deterrence: Denial and punishment

Deterrence is broadly defined as “the practice of discouraging or restraining someone — in world politics, usually a nation-state — from taking unwanted actions, such as an armed attack.”⁸This “practice” typically relies on military capabilities. Most studies of deterrence distinguish between two different approaches: deterrence by denial and deterrence by punishment. Deterrence by denial attempts to minimize the likelihood that an unwanted action — e.g., an invasion — succeeds. As political scientist Michael Mazarr notes, “Deterrence by denial represents, in effect, simply the application of an intention and effort to defend some commitment.”⁹ 

In contrast, deterrence by punishment threatens severe penalties in response to an aggressive act. “The focus of deterrence by punishment,” Mazarr writes, “is not the direct defense of the contested commitment but rather threats of wider punishment that would raise the cost of an attack.”¹⁰Deterring a North Korean invasion, for example, has incorporated elements of both denial and punishment strategies. The U.S.–ROK alliance maintains significant conventional capabilities to respond to and defeat a North Korean invasion (denial) while also possessing tools — e.g., economic sanctions, nuclear strikes, or other regime change operations — that would impose severe penalties on North Korea (punishment).

Conventional wisdom on deterrence has long assumed that military superiority would enable a state to dominate the “ladder of escalation”¹¹in a militarized dispute by convincing its opponent that any reciprocal escalation is a losing bet.¹²The deterrence literature refers to this condition as “escalation dominance.” Militarily speaking, “escalation dominance” is precisely the condition that the U.S.–ROK alliance has met. Despite notable advancements in North Korean nuclear and missile capabilities, experts generally agree that the alliance possesses comprehensive and significant military advantages over North Korea.¹³As of 2023, South Korea’s defense budget — reported at $48 billion — was larger than North Korea’s entire gross domestic product, estimated at around $23 billion.¹⁴

However, deterrence is not only a function of capabilities but also will. This is why the late political scientist and deterrence theorist Thomas Schelling characterized deterrence as the “manipulation of risk,” observing that deterrence is not only about military strength but also the resolve to carry out threats despite the risks of doing so.¹⁵In accordance with Schelling’s logic, the U.S.–ROK alliance’s “general war” deterrence against North Korea is credible. The alliance has both the military capability and the resolve to respond to and defeat a large-scale offensive — conventional or nuclear — against South Korea. North Korea understands that a war against South Korea and the United States would pose serious threats to its regime’s rule and would be best to avoid.¹⁶

North Korea’s risk tolerance and challenges to U.S.–ROK deterrence

This U.S.–ROK superiority has resulted in a highly asymmetric deterrence relationship; the United States and South Korea can credibly threaten North Korea’s existence, but North Korea cannot do the same in return. This imbalance of threats — though it has prevented the outbreak of general war — has created an existential rationale for North Korea to pursue nuclear weapons and practice an extremely risk-acceptant form of deterrence.¹⁷Indeed, North Korea has a long history of defying pressure, initiating crises, and engaging in deliberately provocative behavior.¹⁸

North Korean provocations have tended to be nonlethal, albeit aggressive and destabilizing.¹⁹At times, however, North Korea has also been willing to use outright violence. North Korea torpedoed the South Korean naval vessel Cheonan in April 2010 and bombarded Yeonpyeong Island in the Yellow Sea later that year. Both incidents resulted in South Korean casualties.²⁰At the time, North Korea was experiencing significant internal instability. Then-leader Kim Jong Il’s health was deteriorating rapidly, and it was unclear who would succeed him.²¹ Externally, Pyongyang appeared vulnerable to pressure. It suffered a defeat in a Nov. 2009 skirmish with ROK naval forces, and there was a growing belief in Seoul and Washington that the Kim regime was on the verge of collapse.²² 

Though there are a number of competing and plausible explanations for North Korea’s actions in 2010, the takeaway is that the North Korean regime can — and often does — engage in reckless, destabilizing behavior (including military action) as a means to demonstrate the strength of its resolve and therefore deterrence.²³What’s more, these actions are often successful. Indeed, in 2010, Washington and Seoul feared triggering a larger conflict and chose not to retaliate against both of Pyongyang’s attacks.²⁴The episodes compelled Seoul to back away from its reported plan to broadcast anti-regime propaganda into North Korea using loudspeakers, which the leadership in Pyongyang regarded as a deeply provocative and direct challenge to its political legitimacy.²⁵South Korea also sought out backchannel diplomacy with North Korea to reduce tensions with the intention of eventually holding a high-level summit.²⁶

The North Korean leadership has a vital interest in demonstrating its ability to escalate against and deter the U.S.–ROK alliance, which it sees as an existential threat. Thus, escalation — and the risk of casualties and economic losses that come with it — is a worthwhile sacrifice if it can sufficiently demonstrate a resolve to not back down. In contrast, South Korea and the United States have a broader spectrum of interests to defend. For both countries, casualties or economic losses in a crisis — not to mention the risk of nuclear escalation — are not worth the potentially steep costs.²⁷There is an imbalance, therefore, of escalatory resolve between North Korea and the U.S.–ROK alliance for matters short of major war and nuclear use.²⁸This imbalance of interests and resolve — combined with the reliance on deterrence by punishment for crises at all levels of the escalation ladder — is putting the stability of deterrence for gray zone aggression at risk if policy changes are not made.

The evolution of U.S.–ROK deterrence by punishment

The U.S.–ROK alliance’s adoption of a more assertive and proactive deterrence posture emphasizing retaliation and punishment dates back to the early 2010s in the aftermath of the North Korean attacks on the Cheonan vessel and Yeonpyeong Island.²⁹A common diagnosis then among security communities in Seoul and Washington was that the alliance’s approach to deterrence was too passive, focusing largely on self-defense against an invasion or nuclear use but not much beyond. Because the U.S.–ROK alliance had always been more preoccupied with avoiding escalation and refrained from strong counteractions, there was concern that the alliance was too docile, enabling North Korea to provoke and escalate as long as it did not cross the threshold of major war or a nuclear attack.³⁰ 

Those concerns over the alliance’s inability to appropriately respond to North Korean gray zone aggression prompted South Korea’s Lee Myung–bak administration to adopt a more punishment-oriented deterrence doctrine that promised “proactive” and “manifold” retaliation against North Korean attacks, particularly small-scale, gray zone military provocations.³¹The doctrinal shift was also accompanied by the development of lethal conventional strike capabilities and strategies tailored for retaliation.³²Since then, successive South Korean administrations — under Presidents Park Geun–hye, Moon Jae–in, and Yoon Suk–yeol — have all embraced deterrence by punishment and worked to champion South Korea’s signature conventional strike posture today guided by the concepts of preemption and massive retaliation, which has been dubbed the Three-Axis System.³³

The Three-Axis System consists of 1) the “Kill Chain” to preemptively destroy North Korean nuclear and missile facilities; 2) the Korean Massive Punishment and Retaliation platform to eliminate North Korea’s nuclear command and control — in particular, leader Kim Jong Un — using precision missile strikes and decapitation operations; and 3) the Korean Air and Missile Defense to neutralize North Korea’s attacks.³⁴The implicit message of the Three-Axis System is that if North Korea resorts to violent escalation like it did in 2010, it will face devastating military responses.³⁵Moreover, Pyongyang better not doubt Seoul’s resolve to respond forcefully; with a sophisticated air and missile defense system that can minimize the damage from North Korean attacks, South Korea can launch retaliatory military actions with more confidence and less risk.³⁶

In parallel with the evolution of South Korea’s deterrence policy, the United States has increased the use of punishment-oriented signals in its extended deterrence rhetoric and practice against North Korea. Although “deterrence by punishment” has always been an essential feature of U.S. extended deterrence against North Korea,³⁷the United States has become increasingly outspoken and clear about its commitment to massive retaliation against the North recently.  

The U.S. Nuclear Posture Review, for example, previously threatened retaliation against adversarial nuclear use without specifying North Korea.³⁸)That is no longer the case. The first Trump administration’s 2017 Nuclear Posture Review explicitly declared that “there is no scenario in which the Kim regime could employ nuclear weapons and survive.”³⁹The Biden administration replicated that language in its 2022 Nuclear Posture Review.⁴⁰From presidential speeches to joint U.S.–ROK statements at high and working levels, threatening regime annihilation against North Korean nuclear use has become a regular feature of U.S. rhetoric vis-à-vis North Korea.⁴¹

The United States has also doubled down on nuclear asset deployments around the Korean Peninsula. In recent years, U.S. nuclear-capable strategic bombers have joined the South Korean air force more regularly to conduct large-scale drills.⁴²Starting in July 2023, U.S. nuclear-armed submarines have resumed periodic rotational deployments to South Korea — deployments that had been on hiatus since the 1980s.⁴³The elevated presence of American nuclear assets in North Korea’s vicinity has represented efforts to reaffirm the United States’ commitment to defending South Korea, as well as its declaratory policy of massive retaliation.

The overall reinforcement of U.S. deterrence by punishment against North Korea has been a natural, and in certain aspects necessary, response to evolving deterrence dynamics on the Korean Peninsula. Over the years, North Korea’s nuclear advancements have come to threaten not only South Korea and U.S. regional allies in the Pacific but also American territory directly — raising the need for demonstrating firm U.S. intent to punish North Korean nuclear use.⁴⁴Conventional escalation risks posed by South Korea’s offensive military posture have demanded shoring up U.S. deterrence by punishment as well. The South Korean posture of disproportionate retaliation, while imposing greater costs on North Korea’s conventional military aggression, has also heightened the danger that a potential military crisis spirals out of control and escalates into a full-blown conflict involving nuclear use. In the face of growing North Korean nuclear threats and rising crisis instability on the Korean Peninsula, bolstering U.S. deterrence by punishment at the nuclear level has served as insurance for South Korea to practice offensive deterrence at the conventional level.

North Korea’s increasingly risk-acceptant nuclear posture

North Korea’s nuclear and missile program has witnessed remarkable advancements in recent years. North Korea has also adopted an overall more offensive and risk-acceptant deterrence posture to counter the U.S.–ROK alliance.⁴⁵In 2021, Kim Jong Un introduced a five-year plan to advance North Korea’s weapons program.⁴⁶The plan called for developing a range of new capabilities to upgrade and diversify North Korea’s nuclear deterrent, including smaller and lighter nuclear weapons for tactical use, new types of strategic weapons and vehicles that can deliver tactical nuclear strikes, and more survivable, solid-fuel intercontinental ballistic missiles, or ICBMs.⁴⁷North Korea has aggressively pursued the five-year plan and has made notable progress in meeting its stated goals.⁴⁸

Pyongyang’s buildup of its tactical nuclear forces, in particular, has created a serious deterrence dilemma for the U.S.–ROK alliance. Since North Korea’s arsenal was limited to high-yield weapons only suitable for fighting large-scale warfighting, its nuclear deterrent options in conventional conflict scenarios short of war remained limited. Pyongyang’s evolving tactical nuclear capabilities, however, could fill this gap and open up room for limited, small-scale nuclear deployment. Tactical nuclear weapons can have a yield as low as less than one kiloton, which can be enough to destroy a narrow target, such as a piece of military infrastructure, and avoid doing damage beyond that.⁴⁹As Pyongyang’s tactical nuclear program has advanced, it has substantially lowered the threshold of North Korean nuclear use and increased its feasibility of nuclear use aimed at deterring the U.S.–ROK alliance’s larger counter-escalation in a conventional conflict.⁵⁰

Another alarming trend in North Korea’s nuclear posture has been the adoption of the doctrine of preemptive nuclear use. Citing increased deployments of U.S. nuclear assets to the Korean Peninsula and Seoul’s evolving conventional strike system among “serious circumstances” endangering security, Pyongyang announced revisions to its nuclear doctrine in Sept. 2022, vowing preemptive nuclear strikes against adversary actions suggesting imminent attacks.⁵¹North Korea had never ruled out first use, but its initial nuclear doctrine from April 2013 primarily stressed the retaliatory function of nuclear weapons.⁵²The 2022 law effectively removed the ambiguity regarding Pyongyang’s willingness to resort to first use if necessary.

North Korea’s development of tactical nuclear capabilities and its doctrine of nuclear preemption can significantly increase risks for the U.S.–ROK alliance to practice deterrence by punishment at the conventional level. In an escalating conflict, Seoul’s strategies of preemptive strikes and overwhelming conventional retaliation — which, from Pyongyang’s perspective, pose overt existential threats and must be deterred — can serve to further incentivize North Korean tactical nuclear use, including preemptive use. For example, North Korea could opt for a limited tactical nuclear strike, then threaten larger attacks on military and civilian targets in South Korea, U.S. regional military bases, as well as the U.S. homeland. In this scenario, Washington will face an extreme dilemma: escalate disproportionately by launching a massive retaliatory operation at the risk of full-blown nuclear war or back down and jeopardize U.S. credibility.

Evaluating the risks of deterrence erosion and failure

In theory, the U.S.–ROK alliance today is willing to accept the risks and costs of escalation by committing to proactive and disproportionate retaliation. However, the fundamental dynamics that encourage the alliance’s risk aversion and North Korea’s risk tolerance remain unchanged. There is a credibility gap between the type of actions South Korea is publicly committed to in order to maintain deterrence and the actions it is actually willing to undertake in a gray zone scenario.

North Korea’s two overriding priorities continue to be the survival of its regime and the maintenance of a credible deterrent against the U.S.–ROK alliance. Casualties and economic damage remain acceptable losses in North Korean escalation calculations. For South Korean and American decision-makers, however, every instance of additional escalation compounds the costs of risks that, at a certain level, become virtually impossible to accept. According to research from RAND, it would only take 12 North Korean artillery pieces to destroy a major South Korean industrial factory located in Paju — a city close to the North–South border — and cause approximately nine billion dollars of economic loss.⁵³Most of South Korea’s key economic centers are concentrated in its north, not far from the border, and are therefore vulnerable to even a slight margin of error in missile defense.

Threats of disproportionate retaliation and regime annihilation are intended to discourage North Korean aggression. But they can also work in the opposite direction, heightening Pyongyang’s fatalism, believing it has been backed into a corner and faces a choice between nuclear escalation and capitulation. Pursuing deterrence by punishment as a blanket strategy for all crises and deterrence scenarios puts the U.S.–ROK alliance in an increasingly fraught position to fulfill its commitments against North Korea and keep its deterrent credible. This is especially the case with the advent of Pyongyang’s preemptive nuclear use policy and its growing tactical nuclear capabilities, which have made nuclear escalation more possible.

Pyongyang, for example, could misperceive Seoul’s supposedly “measured” retaliatory action — such as striking a piece of North Korean military infrastructure — as part of a larger offensive aimed at regime annihilation due to South Korea’s preemptive strike posture and policy of preventive decapitation.⁵⁴Pyongyang would have undesirably high incentives for forms of nuclear escalation to deter the alliance from further military action. For instance, Pyongyang could respond with a “limited” tactical nuclear strike on a non-civilian target in South Korea to coerce the alliance into de-escalation. The U.S.–ROK alliance would then face two unacceptable choices: climb higher up the escalation ladder, increasing the risk of a larger nuclear war, or back down in the face of North Korean nuclear use. Both choices would result in a devastating deterrence failure for the alliance.

The dilemma with deterrence by punishment is that not only does it raise the risk of nuclear escalation but it also creates costs and penalties for the alliance’s restraint. Exercising restraint of varying levels against North Korean aggression — whether by responding strictly proportionately, just mildly enough to save face, or not at all — is inconsistent with the alliance’s commitment to disproportionate punishments and massive, regime-ending retaliation, and stark inconsistencies in rhetoric and action degrade the credibility of deterrence. If, however, the alliance were not committed to deterrence by punishment in the first place, exercising restraint would not be at odds with the alliance’s military strategy and would increase its freedom of maneuver during a crisis.

Stabilizing deterrence: De-emphasizing punishments and shifting to denial-oriented deterrence

The crux of deterrence is its credibility. What is vital is that others believe that any issued threats will be followed through on — not how big and loud the threats are. To maintain the credibility of U.S.–ROK deterrence vis-à-vis North Korea, the alliance should curtail its reliance on hair-trigger military actions that are difficult and costly to practice in gray zone crises short of war. This includes preemptive strikes and regime annihilation.⁵⁵Instead, the alliance should focus on “denying” — or lowering the effectiveness of — North Korean aggression by emphasizing and buttressing defensive capabilities. The alliance should also move away from the principle of disproportionate, overwhelming retaliation for scenarios short of a North Korean invasion or nuclear attack and take a more flexible approach that seeks to respond proportionately and avoid escalation.

Shifting to a more denial-oriented form of deterrence demands a range of adjustments to the alliance’s military posture and rhetoric. It is essential that the U.S.–ROK alliance avoids actions that feed into North Korea’s already existential threat perceptions, which play a decisive role in its crisis decision-making and the requisite “necessity” of escalation.⁵⁶

Reorienting South Korea’s conventional posture around denial

South Korea should roll back its preemptive strike posture and only use massive retaliation as a last resort to deter a North Korean invasion or nuclear attack. A South Korean deterrence posture that more clearly reflects a defensive orientation would reduce the likelihood of miscalculation and any consequent overreactions. Maintaining sufficient second-strike and conventional capabilities for wartime readiness will still be necessary. However, South Korea should focus first and foremost on enhancing defensive capabilities and the overall resiliency of U.S.–ROK forces to North Korean attacks. Two notable areas of exploration include basing infrastructure and missile defense.  

Hardening and diversifying U.S.–ROK military facilities in South Korea, as well as ensuring the necessary preparation for rapid infrastructure repair, would strengthen the survivability of U.S.–ROK forces against North Korean attacks and allow them to continue operating in the event of a contingency. This could include building additional ports, airstrips, aircraft shelters, and underground munitions and fuel storage. Strengthening the survivability of U.S.–ROK forces in this manner would diminish the strategic benefits for North Korea to target critical U.S.–ROK military sites during a crisis at the risk of triggering a larger war.⁵⁷

Missile defense is no silver bullet. Nonetheless, it contributes directly to resilience against North Korean attacks by intercepting and destroying missile strikes. U.S.–ROK missile defense has steadily improved in recent years, with South Korea’s development of advanced indigenous missile defense systems⁵⁸and refined allied coordination as a result of regular joint antimissile drills.⁵⁹South Korea should continue to improve its missile defense and rely on it for “denying” North Korean aggression instead of relying on it as insurance to safely launch retaliatory actions against North Korea.

Adjusting joint military exercises, U.S. asset deployment, and rhetoric in line with denial

The United States and South Korea should adjust their joint military exercises, the deployment of U.S. nuclear assets, and allied rhetoric to align more closely with the principles of deterrence by denial. 

Joint exercises are essential for maintaining and increasing operational readiness. However, there is little empirical evidence that joint military exercises deter North Korean aggression. In fact, the track record suggests otherwise, demonstrating that there are aspects of these exercises that can provoke North Korea to engage in saber-rattling and other destabilizing responses. North Korea often views exercises — either in whole or in part — as a legitimate threat requiring a reciprocal demonstration of resolve. Research has also found that the intensity of North Korean responses to joint military exercises varies with the threat level posed by those exercises.⁶⁰

The U.S.–ROK alliance should carefully weigh the benefits of those aspects of joint exercises against their negative consequences for crisis dynamics. The goal should be to find a sweet spot that preserves military readiness without eroding crisis stability.⁶¹A more denial-oriented joint exercise program would give prominence to the kinds of exercises and practices aimed at neutralizing North Korean aggression and minimizing damage — including antimissile drills — and minimize those that involve overt offensive threat signaling. Special operation drills for wartime contingency missions, which may include leadership assassination, should be practiced in secrecy.⁶²

For instance, the U.S.–ROK alliance can benefit from decreasing the deployments of U.S. nuclear assets to the Korean Peninsula, as well as their involvement in joint exercises.⁶³Displaying U.S. nuclear assets in the vicinity of North Korea is intended to clearly demonstrate the U.S. extended deterrence commitment to South Korea while sending a not-so-subtle threat to North Korea. There is a need for these practices to remain in place at a certain level, given their significance as signals of both deterrence and ally reassurance. However, deploying U.S. nuclear assets too often in a regularized, programmed manner can also be counterproductive for both deterrence and ally reassurance.⁶⁴

U.S. nuclear assets lack credibility as a signal of resolve against nonnuclear provocations or attacks by North Korea, because it is unlikely in reality that the United States would want to wage a full-blown nuclear war by employing nuclear assets against North Korean conventional, gray zone escalation. Moreover, while the U.S.–ROK alliance wants to deter and prevent North Korean nuclear use, constant U.S. deployments of nuclear assets can do more to convince North Korea that it should be prepared to use nuclear weapons in conflicts.

The presence of U.S. nuclear assets might reassure South Korea at that moment. However, the sense of relief tends to diminish once those assets leave South Korea, and North Korea ramps up saber-rattling again. Ultimately, repeating this process of reassuring South Korea through making overt nuclear threats has proved limited in effect — as evidenced by the apparent lack of improvement in South Korean public confidence in U.S. extended deterrence despite heightened U.S. nuclear threat signaling against North Korea⁶⁵and persistently strong South Korean demands for independent nuclear weapons.⁶⁶It can also chip away at the credibility of U.S. extended deterrence by creating exaggerated or false South Korean expectations of U.S. nuclear retaliation against North Korea.

A more effective way of deploying U.S. nuclear assets could be to practice selectively and proportionally against particular types of North Korean saber-rattling that the alliance would respond with a massive retaliatory response in a real conflict scenario — for example, North Korean nuclear tests or ICBM tests.⁶⁷This way, the U.S.–ROK alliance can signal clear threats of punishment while avoiding unnecessarily escalating peacetime tensions by giving North Korea regular pretexts for saber-rattling. 

After all, North Korea understands that U.S.–ROK combined forces far outweigh its own and that a war with the alliance would be existential — even if joint military exercises are not always practiced at maximum scale and tempo, American nuclear assets are not showing up constantly on North Korea’s doorstep, and alliance joint statements are not swearing regime-ending retaliation against its attacks all the time.    

Responding to North Korea’s gray zone aggression: Flexibility and proportionality

One potential but valid concern about adopting a more denial-oriented deterrence for conventional military crises is that it could embolden North Korea’s brinkmanship, allowing it to engage in gray zone aggression and dominate the ladder of escalation because the regime understands that there is a hard limit for any U.S.–ROK response. That concern, however, misunderstands why Pyongyang engages in gray zone aggression in the first place. In fact, this potential deterrence shift could better position the alliance to respond to North Korea’s gray zone escalation while also mitigating the rationale for that type of escalation in the first place. 

It is the constant threat of overwhelming punishment that exacerbates North Korea’s existential fears before and during a crisis. That fear incentivizes their use of escalation as a tactic of deterrence, increasing the risk of a broader conflict. Moreover, when punishment is the only military option for the alliance during gray zone crises, it forces the United States and South Korea to decide between two extreme options: escalate unnecessarily or back down entirely.

Deterrence by denial, with its overarching objective being the maintenance of resilience and wartime readiness, does not require hitting North Korea back with overwhelming military force in order for the deterrent to remain credible. Deterrence by denial provides the U.S.–ROK alliance with greater policy flexibility — choosing between military or nonmilitary options — and the ability to keep any response proportional to the gray zone aggression at hand.⁶⁸This would make future gray zone crises more predictable and escapable.

One of the benefits of the proposed denial-oriented deterrence posture is that it is proactive, as it places action — calibrated proportionately — at the center of the alliance’s strategy. Its proactive nature distinguishes it from the alliance’s posture prior to 2010, which was fundamentally passive; the alliance attempted to avoid escalation by refraining from retaliation. This distinction lessens the risk that North Korea would be able to initiate crises expecting that the alliance would not respond, as it did prior to 2010. 

There is no scientific formula to develop a perfect proportional response. What “proportionality” means in a given instance is dependent on the context of the crisis itself. Moreover, proportionality is in the eye of the beholder. There is still the risk that a “proportionate” response in the eyes of the United States and South Korea is, in the eyes of North Korea, highly escalatory. Finding the proportional sweet spot — meeting the minimum threshold to preserve deterrence while avoiding cornering Pyongyang — will require practice and refinement over time. In short, there is no policy response that completely eliminates the element of risk from deterrence. Nonetheless, committing to proportional responses rather than overwhelming punishments will considerably reduce the already high level of risk that the deterrence relationship currently faces.

Beyond deterrence: Arms control and stable coexistence with North Korea

Deterrence, when viewed holistically, is not purely a question of military capabilities. Another crucial part of the overall deterrence process is reassurance: persuading North Korea that military confrontation with the U.S.–ROK alliance is as “unnecessary” as it is ineffective and costly and that the alternative to an aggressive nuclear buildup and posturing is more attractive. Such persuasion will require offering credible reassurances that the alliance’s intentions are defensive and that North Korea’s restraint will be reciprocated and rewarded.⁶⁹Without the process of persuasion and reassurance, deterrence may very well remain incomplete and unstable. Persistent mutual hostility and distrust between the alliance and North Korea will keep both sides prone to misperceptions, miscalculations, and inadvertent escalation. The denial-oriented deterrence posture proposed in the previous section is intended to accomplish the aim of reassurance.

However, deterrence must also be accompanied by proactive diplomacy designed to create a more durable foundation for mutual restraint and stable coexistence. To increase the likelihood of successful diplomatic negotiations with North Korea, the United States and South Korea should shift the goal of negotiations from denuclearization to arms control.⁷⁰

Totally eliminating North Korean nuclear threats through denuclearization is, of course, the ideal case to maximize security on the Korean Peninsula. But this maximalist goal has come with increasing dangers of military confrontation with North Korea. It has guided the United States and South Korea to rely heavily on the coercive strategies of military pressure and sanctions to compel a reluctant North Korea into disarmament, which Pyongyang has often responded to by leveling up threats. North Korea’s belligerence has, in turn, provoked the U.S.–ROK alliance and tested American and South Korean patience, at times driving them toward reckless ideas — e.g., preventive war — to deter and denuclearize the North.⁷¹

Though there have been moments when North Korea caved into pressure and complied with calls for disarmament talks, maximalist goals have often hampered negotiations.⁷²For North Korea, denuclearization means tying its hands and putting itself at the mercy of a far more powerful U.S.–ROK alliance. Because denuclearization is fundamentally antithetical to North Korea’s goal for diplomacy (regime security), seeking diplomatic negotiations with Pyongyang conditioned on denuclearization has, as one analyst put it, incentivized “a cynical form of engagement.”⁷³This cynical engagement has eliminated North Korea’s incentives to view negotiations in a positive-sum manner and has encouraged bad-faith negotiating, increasing the risk of broken promises.⁷⁴The maximalist goal of denuclearization has also justified North Korea in insisting on ambitious goals of its own that the alliance finds hard to accommodate, which has encouraged the alliance’s own “cynical engagement” in negotiations.⁷⁵

The prospects for North Korea’s denuclearization look grim. As of Jan. 2024, North Korea was estimated to have developed approximately 50 nuclear weapons and possess fissile materials for up to approximately 40 more nuclear devices.⁷⁶While North Korea may have been willing to denuclearize for a specific price in the past, those days appear long gone. Pyongyang now insists that conditioning security negotiations on denuclearization itself is a nonstarter, saying it will “never give up nuclear weapons.”⁷⁷Whether this hard-line position is moveable is unclear. But it is obvious that Pyongyang’s bar for considering — let alone entering — negotiations will only increase as its arsenal expands.

Geopolitical conditions are also working increasingly against the goal of denuclearizing North Korea. Russia’s isolation from the West following its full-scale invasion of Ukraine in Feb. 2022 has opened up opportunities for Pyongyang to elevate strategic cooperation with Moscow and further blunt the international sanctions regime, reducing the North Korean regime’s incentives for negotiations.⁷⁸China has kept its distance from the emerging North Korea–Russia partnership, but Beijing has also been uninterested in applying harsher sanctions and political pressure on Pyongyang. There seems to be little to gain and more to lose for China if it were to ramp up pressure against North Korea. Facing growing regional security tensions with the United States externally while also dealing with difficult economic challenges internally,⁷⁹Beijing appears to be in no position to provoke a belligerent Pyongyang on its doorstep.⁸⁰

Given the unrealistic nature of North Korea’s denuclearization, the United States and South Korea should drop it as a goal, at least for the foreseeable future. Instead, Washington and Seoul should center negotiations around tension reduction and arms control, aimed at lowering escalation risks and limiting Pyongyang’s nuclear capabilities and use.⁸¹Dropping denuclearization as a declared goal does not suggest or require formally accepting North Korea’s nuclear power status.⁸²Rather, it is a reshuffling of security priorities according to the evolving reality of the Korean Peninsula: Managing North Korean nuclear threats is becoming increasingly urgent while the prospect of denuclearization diplomacy is only fading away. Admitting the bitter reality that the long-standing aspiration of denuclearizing North Korea is unlikely to arrive anytime soon will not be easy, but mitigating North Korean nuclear threats through arms control would nonetheless improve the security environment around the Korean Peninsula.⁸³

Specific road maps for arms control can vary, but some general measures to consider include: capping North Korea’s further production of nuclear weapons and missiles, restricting particularly escalatory and destabilizing North Korean nuclear programs (notably tactical nuclear weapons), mutually abandoning preemptive doctrines, rolling back forward deployments and military activities in the inter–Korean border area, and moratoriums on North Korean capability testing and U.S.–ROK joint exercises.⁸⁴Simultaneously, sanctions against North Korea can be lifted and inter–Korean joint economic projects can be restarted step-by-step in accordance with any arms control progress.

North Korea could find incentives in such security negotiations centered around arms control and tension reduction, considering its strong aspirations for economic development and its presumable interest in avoiding war with the U.S.–ROK alliance.⁸⁵Combined with a more denial-oriented U.S.–ROK military posture, arms control and tension reduction agreements between the alliance and North Korea would further stabilize the overall deterrence dynamic on the Korean Peninsula — reducing the risk of nuclear escalation, improving crisis management, and increasing mutual transparency of intentions — and would create a more durable foundation for stable coexistence.

Authors

James Park

Research Associate

James Park is a research associate at the Quincy Institute’s East Asia Program. His research interests include South Korean foreign policy and domestic politics, Chinese security issues, and U.S. policy vis-à-vis East Asia.

1. Deterrence by punishment can and often does include other types of penalties (e.g., economic sanctions). In the specific case of the U.S.–ROK alliance, however, the penalties are fundamentally military. For a discussion of the alliance’s doctrine of deterrence by punishment, see “The State of Deterrence on the Korean Peninsula” below. For a broader discussion of the concept of deterrence by punishment, see Michael J. Mazarr, “Understanding Deterrence,” RAND, April 19, 2018, https://www.rand.org/pubs/perspectives/PE295.html. ↩

2. Lawrence Freedman, The Evolution of Nuclear Strategy (New York: St. Martin’s Press, 1989), 112. ↩

3. Immediate deterrence, in the definition of political scientist Michael Mazarr, “represents short-term, urgent attempts to prevent a specific, imminent attack.” Mazarr, “Understanding Deterrence,” 4. ↩

4. Chung-in Moon, “A New Korean War Is Not Imminent. Accidental Escalation Might Be,” National Interest, Feb. 1, 2024, https://nationalinterest.org/blog/korea-watch/new-korean-war-not-imminent-accidental-escalation-might-be-209015; Markus Garlauskas and Lauren D. Gilbert, “Deterrence Is Crumbling in Korea: How We Can Fix it,” Atlantic Council, Nov. 2023, https://www.atlanticcouncil.org/in-depth-research-reports/report/deterrence-is-crumbling-in-korea-how-we-can-fix-it; National Intelligence Council, “North Korea: Scenarios for Leveraging Nuclear Weapons Through 2030,” National Intelligence Estimate, Jan. 2023, https://www.dni.gov/files/ODNI/documents/assessments/NIC-Declassified-NIE-North-Korea-Scenarios-For-Leveraging-Nuclear-Weapons-June2023.pdf. ↩

5. The majority of crises between the U.S.–ROK alliance and North Korea — the Democratic People’s Republic of Korea, or DPRK — fall into this category. Note that the United States has deliberately not specified what acts define a nuclear attack, saying only that “any nuclear attack by the DPRK … against the United States or its allies … will result in the end of that regime” (emphasis added). It is unclear whether other uses of nuclear weapons by the DPRK — e.g., the detonation of a tactical nuclear weapon against uninhabited South Korean territory that does not cause casualties — would merit the “end of that regime.” See U.S. Department of Defense, “Joint Press Statement on the Fourth Nuclear Consultative Group Meeting,” Jan. 10, 2025, https://www.defense.gov/News/Releases/Release/Article/4026575/joint-press-statement-on-the-fourth-nuclear-consultative-group-meeting/. ↩

6. These two acts of aggression fall under the category of “strategic deterrence.” See Garlauskas and Gilbert, “Deterrence Is Crumbling in Korea. ↩

7. This brief’s use of “gray zone” aggression is broader than is typical as it includes attributable uses of force so long as they remain under the threshold of a) an outright invasion of South Korea, and/or b) a nuclear strike against targets in South Korea, the United States, or U.S. regional military bases. For a more typical definition of gray zone aggression, see Michael J. Mazarr et al., “What Deters and Why: Applying a Framework to Assess Deterrence of Gray Zone Aggression,” RAND, April 19, 2021, https://www.rand.org/pubs/research_reports/RR3142.html. ↩

8.  Mazarr, “Understanding Deterrence,” 2. ↩

9. Mazarr, “Understanding Deterrence,” 2. ↩

10. Mazarr, “Understanding Deterrence,” 2 ↩

11. The “escalation ladder,” a concept popularized by military strategist Herman Kahn, is a metaphorical representation of how conflicts can escalate, with each rung representing a distinct level of escalation. Herman Kahn, On Escalation: Metaphors and Scenarios (New York: Frederick A. Praeger, 1965 ↩

12. Forrest E. Morgan et al., Dangerous Thresholds: Managing Escalation in the 21st Century (Santa Monica: RAND, 2008), 15, https://www.rand.org/pubs/monographs/MG614.html; Michael Fitzsimmons, “The False Allure of Escalation Dominance,” War on the Rocks, Nov. 16, 2017, https://warontherocks.com/2017/11/false-allure-escalation-dominance. ↩

13. Terence Roehrig and David Logan, “Deterring a Nuclear North Korea: What Does the Theory Tell Us?” 38 North, Oct. 17, 2024, https://www.38north.org/reports/2024/10/deterring-a-nuclear-north-korea-what-does-the-theory-tell-us; Mazarr et al., “What Deters and Why”; Adam Mount, “Conventional Deterrence of North Korea,” Federation of American Scientists, Dec. 18, 2019, https://fas.org/publication/conventional-deterrence-of-north-korea. ↩

14. Hyun–bin Kim, “Korea’s Defense Spending Ranks 11th Globally,” Korea Times, Jan. 13, 2025, https://www.koreatimes.co.kr/southkorea/defense/20250113/koreas-defense-spending-ranks-11th-globally; Anton Sokolin, “North Korean Economy Grows for First Time in Four Years in 2023: Bank of Korea,” NK News, July 29, 2024, https://www.nknews.org/2024/07/north-korean-economy-grows-for-first-time-in-four-years-in-2023-bank-of-korea/. ↩

15. Thomas C. Schelling, Arms and Influence (New Haven: Yale University Press, 2008), 92–125, https://doi.org/10.12987/9780300186703-004. ↩

16. The leadership in North Korea is well aware of U.S. military operations that eliminated the ruling regimes in, for example, Iraq, Afghanistan, and Libya. Indeed, Pyongyang has warned Washington that North Korea “is neither the Balkans nor Iraq and Libya.” See KCNA, “Spokesman for Supreme Command of KPA Clarifies Important Measures to Be Taken by It,” KCNA Watch, March 5, 2013, https://kcnawatch.org/newstream/1451895555-935842349/spokesman-for-supreme-command-of-kpa-clarifies-important-measures-to-be-taken-by-it. Similarly, a senior North Korean diplomat once expressed concern that the U.S. would treat North Korea as it did “Yugoslavia or Afghanistan’s Taliban, to be beaten to death.” Quoted in Charles L. Pritchard, Failed Diplomacy: The Tragic Story of How North Korea Got the Bomb (Washington, D.C.: Brookings Institution Press, 2007), 38, https://www.brookings.edu/books/failed-diplomacy. ↩

17.  Van Jackson, Rival Reputations: Coercion and Credibility in U.S.–North Korea Relations (Cambridge: Cambridge University Press, 2016), https://doi.org/10.1017/CBO9781316459669; Abby Fanlo and Lauren Sukin, “The Disadvantage of Nuclear Superiority,” Security Studies 32, no. 3 (2023): 446–75, https://doi.org/10.1080/09636412.2023.2225779; Patrick M. Cronin, “Fear and Insecurity: Addressing North Korean Threat Perceptions,” Hudson Institute, March 16, 2021, https://www.hudson.org/foreign-policy/fear-and-insecurity-addressing-north-korean-threat-perceptions. ↩

18. Michael McDevitt, “Deterring North Korean Provocations,” Brookings Institution, Feb. 7, 2011, https://www.brookings.edu/articles/deterring-north-korean-provocations. ↩

19.  Nonlethal provocations have commonly included nuclear tests, missile and artillery firings into contiguous waters, border intrusions around the demilitarized zone, and more. ↩

20. Jack Kim, “North Korea Torpedoed South’s Navy Ship: Report,” Reuters, April 22, 2010, https://www.reuters.com/article/idUSTRE63L08W; Mark McDonald, “‘Crisis Status’ in South Korea after North Shells Island,” New York Times, Nov. 23, 2010, https://www.nytimes.com/2010/11/24/world/asia/24korea.html. ↩

21. Se–jeong Kim, “Kim Jong–ils [sic] Health Deteriorates,” Korea Times, May 5, 2010, https://www.koreatimes.co.kr/www/nation/2024/10/113_65394.html; Yoichi Funabashi, “Dangers Lurk in North Korea’s Leadership Transition,” East Asia Forum, July 27, 2010, https://eastasiaforum.org/2010/07/27/dangers-lurk-in-north-koreas-leadership-transition. ↩

22. Sang–hun Choe, “Korean Navies Skirmish in Disputed Waters,” New York Times, Nov. 10, 2009, https://www.nytimes.com/2009/11/11/world/asia/11korea.html; Leon V. Sigal, “WikiLeaks Reveals South Korean Hopes, Not North Korean Realities,” 38 North, Feb. 10, 2011, https://www.38north.org/2011/02/wikileaks-reveals-south-korean-hopes-not-north-korean-realities; Hyun Park, “Report: U.S. and China Officials Discussed Contingencies for North Korea,” Hankyoreh, Jan. 14, 2014, https://english.hani.co.kr/arti/english_edition/e_northkorea/619667.html. ↩

23. Hyung–joong Park, “북한은 왜 천안함을 공격했을까?: 기존 의견의 검토와 의문점” [“Why Did North Korea Attack the Cheonan? Reviewing the Opinions and Raising Some Questions”], Korean Institute for National Unification, June 4, 2010, https://repo.kinu.or.kr/handle/2015.oak/1651. ↩

24. Then–ROK President Lee Myung–bak was known to consider retaliating against North Korea but ROK military officials reportedly pushed back against the idea. U.S. President Obama and White House officials also reportedly exchanged phone calls with Seoul to prevent further South Korean military actions. “Ex–President Lee Ordered All-Out Retaliation after North’s Yeonpyeong Bombardment in 2010,” Yonhap, Dec. 13, 2015, https://en.yna.co.kr/view/AEN20151213000900315; Agence France Presse, “Gates: America Prevented a ‘Very Dangerous Crisis’ in Korea in 2010,” Business Insider, Jan. 14, 2014, https://www.businessinsider.com/robert-gates-south-korea-airstrike-north-korea-2014-1. ↩

25. Min–hyuk Park, “실질적 北타격 카드 ‘심리전 재개’ 포기” [“South Korea decides to not resume psychological warfare against North Korea”], Dong–A Ilbo, Nov. 26, 2010, https://www.donga.com/news/Politics/article/all/20101126/32876169/2; Victor Cha, “Kim Jong Un Versus the Loudspeaker,” Foreign Policy, Aug. 26, 2015, https://foreignpolicy.com/2015/08/26/kim-jong-un-versus-the-loudspeaker. ↩

26. “S. Korea’s Peace Overture to North,” Al Jazeera, Feb. 1, 2011, https://aje.io/tysq7; Aidan Foster–Carter, “Hitting Below the Belt: Pyongyang Spills the Beans on Secret Summit Talks,” 38 North, July 8, 2011, https://www.38north.org/2011/07/aidanfc070811/. ↩

27. According to Bloomberg, a full-scale conflict on the Korean Peninsula could leave millions dead and cost the global economy $4 trillion in the first year, or 3.9 percent of GDP — more than double the damage from Russia’s invasion of Ukraine. In one year, South Korea’s economy would shrink by 37.5 percent. “Putin, Kim and the $4 Trillion Threat on Cold War’s Last Frontier,” Bloomberg, July 28, 2024, https://www.bloomberg.com/graphics/2024-korea-war-threatens-trillions-for-global-economy. ↩

28. “Nuclear use” here refers to nuclear use for hostile military purposes rather than a test or exercise. ↩

29. Sang–woo Rhee, “From Defense to Deterrence: The Core of Defense Reform Plan 307,” CSIS, Sept. 7, 2011, https://www.csis.org/analysis/defense-deterrence-core-defense-reform-plan-307; Hyuk–chul Kwon, “President Lee Has Changed His Position from Controlled Response to Manifold Retaliation,” Hankyoreh, Nov. 24, 2011, https://english.hani.co.kr/arti/english_edition/e_northkorea/450423.html. ↩

30. Abraham M. Denmark, “Proactive Deterrence: The Challenge of Escalation Control on the Korean Peninsula,” Korea Economic Institute, Dec. 2011, https://keia.org/sites/default/files/publications/proactive_deterrence_paper.pdf; McDevitt, “Deterring North Korean Provocations.” ↩

31. Denmark, “Proactive Deterrence”; McDevitt, “Deterring North Korean Provocations.” ↩

32. The efforts moved in coordination with the United States. In a 2010 joint statement, the two allies announced that “South Korea will continue to build reliable interoperable response capabilities … and that both sides will further interoperability of the alliance’s command and control system.” See Karen Parrish, “U.S., South Korea Announce ‘Tailored Deterrence’ Strategy,” United States Forces Korea, Oct. 3, 2013, https://www.usfk.mil/Media/Newsroom/News/Article/600966. Also in a 2015 joint statement, the alliance confirmed that, “[i]n order to strengthen the combined defense posture, the ROK is in the process of securing major capabilities necessary to develop its own Kill-Chain and Korean Air Missile Defense (KAMD) systems, which will be interoperable with Alliance systems.” See Office of the Press Secretary, “Joint Fact Sheet: The United States–Republic of Korea Alliance: Shared Values, New Frontiers,” The White House, Oct. 16, 2015, https://obamawhitehouse.archives.gov/the-press-office/2015/10/16/joint-fact-sheet-united-states-republic-korea-alliance-shared-values-new. ↩

33. Lami Kim, “A Hawkish Dove? President Moon Jae-in and South Korea’s Military Buildup,” War on the Rocks, Sept. 15, 2021, https://warontherocks.com/2021/09/a-hawkish-dove-president-moon-jae-in-and-south-koreas-military-buildup; Republic of Korea Ministry of National Defense, “2022 ROK Defense White Paper,” June 2023, 57–62, https://www.mnd.go.kr/user/mndEN/upload/pblictn/PBLICTNEBOOK_202307280406019810.pdf; Clint Work, “Navigating South Korea’s Plan for Preemption,” War on the Rocks, June 9, 2023, https://warontherocks.com/2023/06/south-koreas-plan-for-preemption. ↩

34. Sungmin Cho, “South Korea’s Offensive Military Strategy and Its Dilemma,” CSIS, Feb. 29, 2024, https://www.csis.org/analysis/south-koreas-offensive-military-strategy-and-its-dilemma. ↩

35. Seung–yeon Kim, “S. Korea Warns N. Korea Will See End of Regime if It Harms Its People,” Yonhap, Oct. 13, 2024, https://en.yna.co.kr/view/AEN20241012003853315; Minji Lee, “New Defense Chief Warns N. Korea Will Face End of Regime in Event of Provocations,” Yonhap, Sept. 6, 2024, https://en.yna.co.kr/view/AEN20240906007151315; Seok–min Oh, “New Defense Minister Vows to Sternly Respond to N.K. Threats, Bolster Alliance with U.S.,” Yonhap, Oct. 7, 2023, https://en.yna.co.kr/view/AEN20231007002151320. ↩

36. We recognize that South Korea already has adequate missile defense — and thus denial — capabilities. The problem, however, is that South Korea currently combines its missile defense with a commitment to punishment for any retaliatory actions it takes. We recommend in the latter section of the brief that South Korea primarily rely on its missile defense capabilities for denying North Korean aggression rather than as a tool for a punishment-oriented retaliatory posture. ↩

37. The U.S. extended deterrence commitment has long been premised on the logic of intolerable punishment that North Korea’s invasion of (or large-scale use of force against) the South would be met with U.S. military intervention, resulting in the end of the North Korean regime. ↩

38. U.S. Department of Defense, “Nuclear Posture Review Report,” April 2010, available via the Internet Archive Wayback Machine at https://web.archive.org/web/20250227001119/https://dod.defense.gov/portals/1/features/defensereviews/npr/2010_nuclear_posture_review_report.pdf (Feb. 27, 2025 ↩

39. Office of the Secretary of Defense, “Nuclear Posture Review,” U.S. Department of Defense, Feb. 2018, 33, available via the Internet Archive Wayback Machine at https://web.archive.org/web/20250207212051/https://media.defense.gov/2018/Feb/02/2001872886/-1/-1/1/2018-NUCLEAR-POSTURE-REVIEW-FINAL-REPORT.PDF (Feb. 7, 2025). ↩

40. U.S. Department of Defense, “2022 National Defense Strategy of the United States of America,” Oct. 2022, 12, https://media.defense.gov/2022/Oct/27/2003103845/-1/-1/1/2022-NATIONAL-DEFENSE-STRATEGY-NPR-MDR.PDF. ↩

41. ROK Ministry of Foreign Affairs, “Washington Declaration,” April 28, 2023, https://www.mofa.go.kr/eng/brd/m_25772/view.do?seq=14; David E. Sanger, “In Turn to Deterrence, Biden Vows ‘End’ of North Korean Regime if It Attacks,” New York Times, April 26, 2023, https://www.nytimes.com/2023/04/26/us/politics/biden-south-korea-state-visit.html; U.S. Department of Defense, “Joint Press Statement on the Fourth Nuclear Consultative Group Meeting,” Jan. 10, 2025,  https://www.defense.gov/News/Releases/Release/Article/4026575/joint-press-statement-on-the-fourth-nuclear-consultative-group-meeting. ↩

42. Pacific Air Forces, “U.S. Strategic Bombers, ROK, U.S. Fighters Conduct Combined Aerial Training,” U.S. Air Force, April 14, 2023, https://www.pacaf.af.mil/News/Article-Display/Article/3363808/us-strategic-bombers-rok-us-fighters-conduct-combined-aerial-training; AP, “South Korea, U.S. Conduct Aerial Exercise Involving B-1B Bomber,” Nikkei Asia, Feb. 20, 2025, https://asia.nikkei.com/Politics/Defense/South-Korea-U.S.-conduct-aerial-exercise-involving-B-1B-bombe. ↩

43. Hyung–jin Kim, “U.S. Deploys Nuclear-Armed Submarine to South Korea in Show of Force Against North Korea,” AP, July 18, 2023, https://apnews.com/0c6a71344452d5b12420c13fd66a5a1f; Hyonhee Shin, “Second U.S. Submarine Arrives in South Korea amid North Korea Tensions,” Reuters, July 24, 2023, https://www.reuters.com/world/asia-pacific/second-us-submarine-arrives-south-korea-amid-north-korea-tensions-2023-07-24; “North Korea Says U.S. Nuclear Submarine at South Korea Port Posing Grave Threat, KCNA Reports,” Reuters, Feb. 11, 2025, https://www.reuters.com/world/asia-pacific/north-korea-says-us-nuclear-submarine-south-korea-port-posing-grave-threat-kcna-2025-02-10. ↩

44. Aaron Miles, “Escalation Dominance in America’s Oldest New Nuclear Strategy,” War on the Rocks, Sept. 12, 2018, https://warontherocks.com/2018/09/escalation-dominance-in-americas-oldest-new-nuclear-strategy ↩

45. While Pyongyang’s exact motives of pursuing a more offensive deterrence posture have been unclear, its existential fears — whether exaggerated or not — facing the alliance’s offensive deterrence posture have ostensibly been a factor. As one analyst suggests, “Kim appears to be doing everything he can to convince South Korea and the United States that decapitation strikes are not possible without severe consequences.” See Bruce W. Bennett, “How Kim Jong–un’s Fears Shape North Korea’s Nuclear Weapons Agenda,” RAND, April 19, 2023, https://www.rand.org/pubs/commentary/2023/04/how-kim-jong-uns-fears-shape-north-koreas-nuclear-weapons.html. ↩

46. KCNA, “On Report Made by Supreme Leader Kim Jong Un at 8th Congress of WPK,” KCNA Watch, Jan. 9, 2021, https://kcnawatch.org/newstream/1610155111-665078257/on-report-made-by-supreme-leader-kim-jong-un-at-8th-congress-of-wpk. ↩

47. For details, see Hans M. Kristensen et al., “North Korean Nuclear Weapons, 2024,” Bulletin of the Atomic Scientists 80, no. 4 (2024): 251–71, https://doi.org/10.1080/00963402.2024.2365013. ↩

48. Hyonhee Shin and Daewoung Kim, “North Korea’s Kim Orders More Production of Weapons-Grade Nuclear Materials,” Reuters, March 28, 2023, https://www.reuters.com/world/asia-pacific/north-koreas-kim-calls-scaling-up-weapons-grade-nuclear-materials-kcna-2023-03-27; Joseph S. Bermudez Jr., Victor Cha, and Jennifer Jun, “North Korea Launches New Ballistic Missile Submarine,” CSIS, Sept. 11, 2023, https://beyondparallel.csis.org/north-korea-launches-new-ballistic-missile-submarine; Cynthia Kim, “North Korea Stages ‘Tactical Nuclear Attack’ Drill,” Reuters, Sept. 3, 2023, https://www.reuters.com/world/asia-pacific/north-korea-says-it-staged-tactical-nuclear-attack-drill-2023-09-02; Hyuk-chul Kwon, “Why N. Korea Is Diversifying Its Missile Launch Platforms,” Hankyoreh, March 27, 2023, https://english.hani.co.kr/arti/english_edition/e_northkorea/1085359.html. ↩

49. Union of Concerned Scientists, “What Are Tactical Nuclear Weapons?” June 1, 2022, https://www.ucs.org/resources/tactical-nuclear-weapons. ↩

50. Ankit Panda, “North Korea’s Tactical Nuclear Plans Are a Dangerous Proposition,” Foreign Policy, April 28, 2022, https://foreignpolicy.com/2022/04/28/north-korea-tactical-nuclear-plans-dangerous-proposition; Adam Mount and Jungsup Kim, “North Korea’s Tactical Nuclear Threshold Is Frighteningly Low,” Foreign Policy, Dec. 8, 2022, https://foreignpolicy.com/2022/12/08/north-korea-tactical-nuclear-threat; Robert E. Kelly, “Why North Korea May Use Nuclear Weapons First, and Why Current U.S. Policy Toward Pyongyang Is Unsustainable,” Bulletin of the Atomic Scientists, Nov. 21, 2023, https://thebulletin.org/2023/11/why-north-korea-may-use-nuclear-weapons-first-and-why-current-us-policy-toward-pyongyang-is-unsustainable. ↩

51. KCNA, “Respected Comrade Kim Jong Un Makes Policy Speech at Seventh Session of the 14th SPA of DPRK,” KCNA Watch, Sept. 10, 2022, https://kcnawatch.org/newstream/1662790085-260921382/respected-comrade-kim-jong-un-makes-policy-speech-at-seventh-session-of-the-14th-spa-of-dprk; Naenara, “DPRK’s Law on Policy of Nuclear Forces Promulgated,” KCNA Watch, Sept. 9, 2022, https://kcnawatch.org/newstream/1662721725-307939464/dprk’s-law-on-policy-of-nuclear-forces-promulgated; Min Joo Kim, “North Korea Codifies Right to Launch Preemptive Nuclear Strikes,” Washington Post, Sept. 9, 2022, https://www.washingtonpost.com/world/2022/09/09/north-korea-nuclear-weapons-kim-jong-un. ↩

52. Tong–hyung Kim, “Kim Warns N. Korea Could ‘Preemptively’ Use Nuclear Weapons,” AP, April 30, 2022, https://apnews.com/56eaaad53cd646d581cf71daae0ee7b6; JH Ahn, “North Korea Says It Will Nuke U.S. at First Sign of Pre-Emptive Strike,” NK News, April 11, 2017, https://www.nknews.org/2017/04/north-korea-says-it-will-nuke-u-s-at-first-sign-of-pre-emptive-strike; KCNA, “Law on Consolidating Position of Nuclear Weapons State Adopted,” KCNA Watch, April 1, 2013, https://kcnawatch.org/newstream/1451896124-739013370/law-on-consolidating-position-of-/Lee. ↩

53.  D. Sean Barnett et al., “North Korean Conventional Artillery: A Means to Retaliate, Coerce, Deter, or Terrorize Populations,” RAND, Aug. 2020, 9–10, https://www.rand.org/pubs/research_reports/RRA619-1.html. ↩

54. Ankit Panda, “South Korea’s ’Decapitation‘ Strategy against North Korea Has More Risks than Benefits,” Carnegie Endowment for International Peace, Aug. 15, 2022, https://carnegieendowment.org/posts/2022/08/south-koreas-decapitation-strategy-against-north-korea-has-more-risks-than-benefits. ↩

55. As stated elsewhere in this brief, rolling back these policy options only applies to gray zone crises short of war. They should be kept available for use to deter or respond to a North Korean invasion of South Korea or North Korean nuclear use. ↩

56. Robert Jervis and Mira Rapp–Hooper, “Perception and Misperception on the Korean Peninsula,” Foreign Affairs 97, no. 3 (May/June 2018): 103–17, https://www.foreignaffairs.com/articles/north-korea/2018-04-05/perception-and-misperception-korean-peninsula. ↩

57. Adam Mount and Andrea Berger, “Report of the International Study Group on North Korea Policy,” Federation of American Scientists, Jan. 4, 2019, 38–39, https://fas.org/publication/report-of-the-international-study-group-on-north-korea-policy. ↩

58. Joo–young Hwang, “South Korea to Develop Indigenous ‘Iron Dome’ System,” Korea Herald, Jan. 20, 2025, https://www.koreaherald.com/article/10402900; Gordon Arthur, “South Korea Preps New Antimissile Weaponry to Counter North’s Arsenal,” Defense News, June 5, 2024, https://www.defensenews.com/global/asia-pacific/2024/06/05/south-korea-preps-new-antimissile-weaponry-to-counter-norths-arsenal; “S. Korea Succeeds in L–SAM Missile Interception Test for 3rd Time,” Korea Herald, June 1, 2023, https://www.koreaherald.com/article/3138009. ↩

59. U.S. Indo–Pacific Command, “U.S., Japan, Republic of Korea Conduct Trilateral Ballistic Missile Defense Exercise,” Aug. 29, 2023, https://www.pacom.mil/Media/News/News-Article-View/Article/3507956; “U.S. Troops in South Korea Step Up Missile Defense Drills,” Kyodo News, March 15, 2022, https://english.kyodonews.net/news/2022/03/7f8a84f6444a-us-troops-in-s-korea-step-up-missile-defense-drills.html. ↩

60. Jordan Bernhardt and Lauren Sukin, “Joint Military Exercises and Crisis Dynamics on the Korean Peninsula,” Journal of Conflict Resolution 65, no. 5 (May 2021): 855–88, https://doi.org/10.1177/0022002720972180. ↩

61. Bernhardt and Sukin, “Joint Military Exercises.” ↩

62. Anna Fifield, “In Drills, U.S., South Korea Practice Striking North’s Nuclear Plants, Leaders,” Washington Post, March 7, 2016, https://www.washingtonpost.com/world/in-drills-us-south-korea-practice-striking-norths-nuclear-plants/2016/03/06/46e6019d-5f04-4277-9b41-e02fc1c2e801_story.html; “S. Korea, U.S. to Hold Drills for N. Korean Leadership Removal and Civilian Support,” Dong–A Il Bo, March 4, 2023, https://www.donga.com/en/article/all/20230304/3998914/1. ↩

63. Joo–young Hwang, “First U.S. Strategic Asset Deployed to Korea under Trump 2.0,” Korea Herald, Feb. 20, 2025, https://www.koreaherald.com/article/10425008; Shreyas Reddy, “U.S., ROK and Japan Hold Nuclear Bomber Drills after North Korean Missile Launch,” NK News, April 2, 2024, https://www.nknews.org/2024/04/us-rok-and-japan-hold-nuclear-bomber-drills-after-north-korean-missile-launch; Hyung–jin Kim, “The U.S. Flies Nuclear-Capable Bombers in a Fresh Show of Force against North Korea,” AP, June 30, 2023, https://apnews.com/ab6d5649f6d171ed8817a971bffe11be; Josh Smith, “North Korea Says U.S. Drills Threaten to Turn Region into ‘Critical War Zone’,” Reuters, Feb. 2, 2023, https://www.reuters.com/world/asia-pacific/north-korea-says-us-drills-have-pushed-situation-extreme-red-line-kcna-2023-02-01. ↩

64. Van Jackson, “The Trouble with the U.S. Bomber Overflight Against North Korea,” The Diplomat, Jan. 12, 2016, https://thediplomat.com/2016/01/the-trouble-with-the-us-bomber-overflight-against-north-korea. ↩

65. Research found that South Korean public confidence in U.S. extended deterrence showed no improvement despite increased U.S. deployments of nuclear assets following the April 2023 U.S.–ROK Washington Declaration. Peter K. Lee and Chungku Kang, “Comparing Allied Public Confidence in U.S. Extended Nuclear Deterrence,” Asan Institute for Policy Studies, March 27, 2024, https://en.asaninst.org/contents/comparing-allied-public-confidence-in-u-s-extended-nuclear-deterrence. ↩

66. Adam Mount, “The U.S. and South Korea: The Trouble with Nuclear Assurance,” Survival 65, no. 2 (2023): 123–40, https://doi.org/10.1080/00396338.2023.2193104; Josh Smith, “Calls for South Korean Nuclear Arsenal Unlikely to Fade Despite U.S. Deal,” Reuters, April 27, 2023, https://www.reuters.com/world/calls-south-korean-nuclear-arsenal-unlikely-fade-despite-us-deal-analysts-say-2023-04-27; Jeongmin Kim, “In Shift, South Korea’s Top Diplomat Says Nuclear Armament ‘Not off the Table’,” NK News, Feb. 27, 2025, https://www.nknews.org/2025/02/in-shift-south-koreas-top-diplomat-says-nuclear-armament-not-off-the-table. ↩

67. Hyung–jin Kim, “U.S. Flies Long-Range Bomber in Drill with South Korea, Japan in Reaction to the North’s Missile Test,” AP, Nov. 3, 2024, https://apnews.com/43b568921a7521468167fe30915cd943. ↩

68.  Nonmilitary options may include joint exercises, sanctions, and diplomatic pressure. ↩

69. Mazarr, “Understanding Deterrence.” ↩

70. Jeffrey Lewis, “It’s Time to Accept that North Korea Has Nuclear Weapons,” New York Times, Oct. 13, 2022, https://www.nytimes.com/2022/10/13/opinion/international-world/north-korea-us-nuclear.html. ↩

71. Van Jackson, On the Brink: Trump, Kim, and the Threat of Nuclear War (Cambridge: Cambridge University Press, 2018), https://doi.org/10.1017/9781108562225; David E. Sanger, “Talk of ‘Preventive War’ Rises in White House over North Korea,” New York Times, Aug. 20, 2017, https://www.nytimes.com/2017/08/20/world/asia/north-korea-war-trump.html; “North Korea: Likelihood of War with U.S. ‘Established Fact’,” VOA, Dec. 7, 2017, www.voanews.com/a/4153282.html. ↩

72. Jeffrey Lewis, “Opinion: Trump Just Walked Away from the Best North Korea Deal He’ll Ever Get,” NPR, March 1, 2019, https://www.npr.org/2019/03/01/698909173. ↩

73. Van Jackson, “Risk Realism: The Arms Control Endgame for North Korea Policy,” Center for a New American Security, Sept. 24, 2019, https://www.cnas.org/publications/reports/risk-realism. ↩

74. Jackson, “Risk Realism.” ↩

75. For example, Pyongyang had demanded complete removal of nuclear threats from not only Washington but also “all neighboring areas” before eliminating its own nuclear capability. Will Ripley, Sophie Jeong, and Matthew Robinson, “North Korea Says It Will Not Denuclearize until the U.S. Eliminates ‘Nuclear Threat’,” CNN, Dec. 20, 2018, https://www.cnn.com/2018/12/20/asia/north-korea-us-nuclear-threat-intl/index.html. ↩

76.  SIPRI Yearbook 2024: Armaments, Disarmament and International Security (Stockholm: Stockholm International Peace Research Institute, 2024), 272, 339, https://www.sipri.org/yearbook/2024. ↩

77. Colin Zwirko and Jeongmin Kim, “Kim Jong Un Says He Will ‘Never Give Up’ Nuclear Weapons, Rejects Future Talks,” NK News, Sept. 9, 2022, https://www.nknews.org/2022/09/kim-jong-un-says-he-will-never-give-up-nuclear-weapons-rejects-future-talks. ↩

78. Samuel Ramani, “From Reluctant Enforcer to Outright Saboteur: Russia’s Crusade against North Korea Sanctions,” 38 North, June 24, 2024, https://www.38north.org/2024/06/from-reluctant-enforcer-to-outright-saboteur-russias-crusade-against-north-korea-sanctions; Tong–hyung Kim, “North Korea and Russia Agree to Expand Their Economic Cooperation,” AP, Nov. 21, 2024, https://apnews.com/a6dd64440b4d451026c0bb32d5235a91. ↩

79. Susan A. Thornton, Li Nan, and Juliet Lee, “Debating North Korea: U.S. and Chinese Perspectives,” 38 North, Aug. 25, 2021, https://www.38north.org/2021/08/debating-north-korea-us-and-chinese-perspectives; Ho–fung Hung, “China’s Long Economic Slowdown,” Dissent, Feb. 6, 2025, https://www.dissentmagazine.org/online_articles/chinas-long-economic-slowdown. ↩

80. China has a keen interest in preserving stability near its border and hence an interest in discouraging North Korea’s escalatory behavior. But that interest also motivates China to limit its pressure on North Korea and avoid provoking the Pyongyang regime. See Leif–Eric Easley, “Why China Takes a Middle-of-the-Road Policy toward North Korea,” Washington Post, Feb. 28, 2019, https://www.washingtonpost.com/politics/2019/02/28/why-china-takes-middle-of-the-road-policy-toward-north-korea. ↩

81. Jackson, “Risk Realism”; Toby Dalton and Jina Kim, “Rethinking Arms Control with a Nuclear North Korea,” Survival 65, no. 1 (2023): 21–48, https://doi.org/10.1080/00396338.2023.2172847. ↩

82. Analysts like Frank Aum and John Carl Baker observe that, while it makes practical sense to put denuclearization on the back burner, the U.S.–ROK alliance should maintain denuclearization as an aspirational long-term goal to ensure the viability of the global nonproliferation regime and to secure domestic political support in the U.S. and South Korea for an arms control deal with North Korea. Frank Aum, “Reconciling the Korean Peninsula’s Dual Nuclear Proliferation Crises,” Arms Control Today, March 2023, https://www.armscontrol.org/act/2023-03/features/reconciling-korean-peninsulas-dual-nuclear-proliferation-crises; John Carl Baker, “North Korean Arms Control Doesn’t Have to Conflict with Disarmament,” United States Institute for Peace, Jan. 19, 2023, via the Internet Archive Wayback Machine at https://web.archive.org/web/20241022040636/https://www.usip.org/publications/2023/01/north-korean-arms-control-doesnt-have-conflict-disarmament (Oct. 22, 2024). ↩

83. Shifting the orientation of negotiations with North Korea from denuclearization to arms control can risk driving South Korea and Japan toward seeking their own nuclear weapons, without close consultations and sufficient allied agreement. While reassuring South Korea and Japan about U.S. defense commitments, the United States will also have to make substantial diplomatic efforts to convince its allies that the new policy direction serves shared security interests. ↩

84. Tension reduction measures regarding border area military activities can be expanded on the scrapped 2018 inter–Korean Comprehensive Military Agreement. Yong–sup Han, “군비통제 관점에서 본 9.19 남북군사합의의 의의와 전망” [“Analysis of the 9/19 South–North Korea Military Agreements from the Perspective of Arms Control Concepts”], 『국가전략』[National Strategy] 25, no. 2 (2019): 5–31, https://doi.org/10.35390/sejong.25.2.201905.001; Kelsey Davenport, “North Korea Ends Inter–Korean Military Agreement,” Arms Control Today, Jan./Feb. 2024, https://www.armscontrol.org/act/2024-02/news/north-korea-ends-inter-korean-military-agreement. ↩

85. Brad Babson, “A Framework for Meaningful Economic Engagement with North Korea,” United States Institute of Peace, Feb. 26, 2024, via the Internet Archive Wayback Machine at https://web.archive.org/web/20241103194925/https://www.usip.org/publications/2024/02/framework-meaningful-economic-engagement-north-korea (Nov. 3, 2024); John Delury, “North Korea in 2019: A Year of Strategic Adjustment,” Asian Survey 60, no.1 (Jan./Feb. 2020): 69–78, https://doi.org/10.1525/as.2020.60.1.69. ↩