全球智库信息集成服务系统

Summary

Regardless of the prospects of denuclearizing North Korea, the United States and South Korea (ROK) are likely to continue strengthening capabilities to deter North Korean coercive behavior. Yet, as they do this, it will become increasingly important to assess the regional implications of their actions. Their efforts have already had, and will continue to have, broad spillover effects, potentially creating new tensions with China and complicating alliance relations with Japan. All of the prospective deterrence options could fuel misperception and lead to further instability in the region.

The Current Situation

• Long-range ballistic missiles now enable North Korea to target the United States’ mainland with nuclear weapons, threatening the credibility of the U.S. commitment to South Korea’s defense.
• Yet defense analysts in South Korea, the United States, Japan, and China have different perceptions of North Korea’s objectives, contributing to uncertainty around the prioritization and effects of potential responses.
• To guard against potential nuclear coercion, Seoul and Washington could deploy new weapons to strike targets in North Korea, build new missile defense systems, and/or station more U.S. nuclear assets in or around South Korea, among other options.
• However, as recent events demonstrate, any option is likely to elicit a regional reaction. In response to Seoul’s decision to permit the United States to deploy the Terminal High-Altitude Area Defense (THAAD) system, China levied informal economic penalties against South Korea in 2017 and warned against any future actions that threaten China’s security.

Weighing Options

• Augmenting U.S. and South Korean offensive weapon systems could flexibly support both preemptive and retaliatory strikes, but ambiguity about the purpose of such weapons could exacerbate crisis instability.
• Strengthening U.S. extended nuclear deterrence, especially through stationing U.S. tactical nuclear weapons on the peninsula, would have broad, long-term effects in the region. And Beijing would most likely view it as part of a geostrategic strategy to contain China.
• Augmenting deterrence against North Korean tactical provocations is less likely to provoke regional reactions than other offensive or defensive options.
• Japan worries about U.S. disengagement from the region and favors enhancing U.S.-ROK-Japan cooperation, whereas China sees such trilateral engagement as a clear threat.
• Having failed to dissuade South Korea from approving the deployment of THAAD, China may exercise stronger retaliatory measures in response to future perceived geostrategic actions.
• Regional track 1.5 or track 2 dialogues could reduce or mitigate long-standing regional distrust by improving the understanding of threat perceptions and other security concerns, as well as helping to recognize when and how future crises might manifest.

Introduction

In 2013, concerned by the growing threat of North Korea’s ballistic missiles to U.S. military personnel and assets stationed in East Asia, U.S. officials approached their South Korean counterparts about stationing Terminal High-Altitude Area Defense (THAAD) missile defense batteries and associated radar systems on South Korean territory. After a protracted and contentious debate, in 2016, the South Korean government announced its decision to proceed with THAAD deployment despite loud “not in my backyard” opposition from residents in Seongju, the site selected for the new system. But the controversy did not end there. The decision reverberated throughout the region.

As South Korean officials weighed the decision to deploy THAAD, Chinese officials voiced concern that the THAAD radar would bolster the ability of U.S. missile defense systems to target Chinese missiles, which they argued constituted a threat to China’s strategic security interests.¹ Chinese concerns evolved into public threats as Seoul inched closer to a THAAD deployment decision. For example, in a meeting with South Korean corporate executives in December 2016, a Chinese foreign ministry official stated that “China would take measures that would come close to breaking off diplomatic ties.”² Following the South Korean decision to proceed with THAAD, China instituted a range of soft yet highly punitive economic sanctions against South Korea and several of its private companies. Chinese tourism to South Korea came to a halt following the institution of a de facto travel ban by Beijing.³ Using intrusive regulatory tactics, such as targeted tax investigations and safety inspections, China forced the closure of nearly all of the South Korean–owned Lotte Mart stores in China, aiming to punish the conglomerate that had agreed to turn over land for the THAAD site.⁴ According to trade figures, exports of South Korean automobiles, cosmetics, and other commodities to China plummeted in 2017.⁵ A report by the Hyundai Research Institute estimated that China’s economic retaliation for THAAD cost the Korean economy $7.6 billion in 2017.⁶ In late 2017, following quiet diplomatic work by the South Korean and Chinese governments to patch relations, China began to back off these punitive measures in return for South Korean promises to limit certain future missile defense activities and to not enter into trilateral defense arrangements with the United States and Japan.⁷

The THAAD episode is likely a harbinger of regional security challenges to come in East Asia. Advances in North Korea’s nuclear and missile capabilities, especially since 2015, have changed the character of deterrence on the Korean Peninsula. As the United States and its allies South Korea and Japan consider responses to the evolving threat from Pyongyang, they risk provoking reactions by China and Russia, thus deepening security dilemmas throughout the region.

Since the beginning of 2018, a diplomatic thaw and unprecedented summitry reduced military tensions and created new hope for a negotiated solution to the challenges presented by North Korea’s pursuit of nuclear and missile capabilities. However, even if a denuclearization process is initiated, North Korea will continue to possess nuclear weapons for the immediate future. In the meantime, the United States, South Korea, and Japan will continue to maintain and perhaps strengthen measures to ensure the credibility of deterrence and to ward against provocations. If diplomacy breaks down, deterrence will again be the primary means of security management in the region.

North Korea’s ability to target not just South Korea or even U.S. military bases in East Asia with nuclear weapons, but now also the U.S. mainland, raises a critical question for policymakers: could this capability embolden more aggressive North Korean behavior? Many South Korean, Japanese, and U.S. officials and experts believe it might. Prudence suggests, therefore, that the allies weigh options to augment defensive and offensive military capabilities to deter future North Korean acts of aggression or coercion. Among other imperatives, Seoul, Washington, and Tokyo need to (1) manage escalation risks arising from low-level provocations; (2) avoid scenarios that could result in first use of nuclear weapons (accidental, unintended, or otherwise); (3) deter interwar escalation; and (4) mitigate the possibility of alliance decoupling should North Korea threaten nuclear attacks on the continental United States.

Addressing three interrelated questions could help to identify, and prepare for, the potential cascading security effects of evolving deterrence on the Korean Peninsula: What are North Korea’s nuclear capabilities and what would its objectives be in using them? What options do South Korea and the United States—individually, through their bilateral military alliance, and in some cases, with Japan—have to respond to this changing threat? And what are the implications of an action-reaction sequence for security in East Asia?

Based on discussions and interviews with dozens of officials and experts in China, Japan, South Korea, and the United States, this paper explores North Korea’s nuclear capability and how it could shape future security in the region. It also considers various notional options that the United States and South Korea (and, in some cases, Japan) could adopt to maintain credible deterrence and guard against nuclear coercion, as well as the possible reactions of Beijing and Tokyo to these options. (Because of its alliance with the United States, Japan is inherently involved in the deterrence of North Korea and will be affected by changes in the regional security environment resulting from U.S.–Republic of Korea, or ROK, actions.) China’s response to the THAAD deployment has made it clear that second-order effects of North Korea’s nuclearization can reverberate throughout the region. Understanding when and why such reverberations might occur is critical to assuring a more secure future for states and polities in East Asia. The analysis could usefully inform potential actions and help determine whether they would stabilize the region or exacerbate existing security dilemmas.

North Korean Nuclear Capabilities

North Korea’s pace of nuclear and ballistic missile testing in recent years demonstrated a faster-than-predicted advancement in its capabilities, while Pyongyang’s prolific propaganda provided analysts considerable insight into the underlying technological achievements and the nuclear program’s future direction. Of course, there are still large knowledge gaps, particularly related to the program’s developmental hurdles, which systems are fully operational, and how these systems might be used. One can assume, however, that similar to other states that have developed nuclear capabilities, North Korea is now faced with resolving tension between the consolidation of technical progress and the achievement of its diplomatic and political objectives. Thus, as the picture of its technical capabilities becomes clearer, so too will its objectives.

Assessing North Korea’s Nuclear Arsenal

It is widely assessed that North Korea is capable of building fission and even boosted fission weapons and fashioning these into warheads. An analysis by the U.S. Defense Intelligence Agency, for instance, reportedly concluded in July 2017 that North Korea successfully produced a miniaturized nuclear warhead that can be installed onto its ballistic missiles.⁸ North Korea also claims to have successfully conducted hydrogen bomb tests and has published pictures of what appears to be a model of a two-stage thermonuclear device. After six nuclear tests, North Korean scientists likely understand the technology to manufacture hydrogen weapons, although their capability to miniaturize the design or produce the weapons serially and reliably remains uncertain.⁹

Much remains unknown about the types and amounts of fissile material utilized in North Korea’s nuclear weapon designs. In 2016, a widely cited assessment conducted by former Los Alamos National Laboratory director Siegfried Hecker and colleagues concluded that North Korea is annually producing fewer than 6 kilograms of plutonium and about 150 kilograms of highly enriched uranium (HEU).¹⁰ Hecker estimated that, by the end of 2017, North Korea could possess 20–40 kilograms of plutonium and 250–500 kilograms of HEU—which is sufficient for roughly twenty-three to thirty nuclear weapons—and might be producing an additional six to seven weapons’ worth of fissile material every year.¹¹ Other Western nongovernmental entities estimated similar ranges.¹² Interestingly, government estimates were slightly higher. For example, a South Korean Ministry of National Defense assessment estimated the North Korean plutonium stockpile at around 50 kilograms by the end of 2016.¹³ The U.S. Defense Intelligence Agency concluded in July 2017 that North Korea could already possess up to sixty nuclear weapons and could produce twelve more weapons every year.¹⁴

In 2013, the pace of North Korea’s ballistic missile development activities accelerated sharply. Since then, it has tested various new systems of increasing range and with different engine technologies and designs. Most notably, in 2017, North Korea tested the Hwasong-14 (KN-20) twice and then surprised the world by conducting a first test launch of the larger Hwasong-15 (KN-22). Although it is unclear whether either of these intercontinental ballistic missiles (ICBMs) is intended for production and operational capability, most analysts believe they could deliver nuclear warheads to the continental United States. And the chairman of the U.S. Joint Chiefs of Staff affirmed during testimony that policymakers should “assume now that North Korea has the capability” to do so.¹⁵ Even if North Korea still lacks the capability to resolve remaining technical obstacles, such as a re-entry vehicle able to withstand intercontinental travel, these obstacles can eventually be surmounted.

The accuracy of existing North Korean ICBM and intermediate-range ballistic missiles is also an open question. Nevertheless, while inaccurate missiles may not be credible threats against small counterforce targets, such as certain military facilities, they are undoubtedly credible against countervalue targets. In addition, North Korea’s short-, medium-, and intermediate-range ballistic missiles have demonstrated the capability to place a wide range of regional targets—population centers and large military bases in South Korea, Japan, and probably Guam—at risk. North Korean scientists will surely work to improve the accuracy of medium- and long-range missiles, providing additional targeting options.

They will also focus on improving survivability of their nuclear arsenal. Despite the high cost of building a credible sea-based nuclear deterrent capability, North Korea seems committed to developing submarine-launched ballistic missiles (SLBMs). Beginning in late 2014, it conducted several land and submerged ejection tests of the Pukkuksong-1 (KN-11) missile. And satellite imagery from 2017 shows continuing work on a second submersible missile test barge and a submarine to carry ballistic missiles.¹⁶ North Korea has made considerable progress in improving the mobility and readiness of its land-based missiles. It has redeveloped medium-range missiles to replace older liquid-fueled engines with solid-fueled ones and has tested various models of transporter erectors and transporter-erector-launchers for moving missiles to launch bases. This fast pace of development seems to be the product of an extensive missile industrial infrastructure that North Korea spent decades to build. Having steadily accumulated the necessary technologies, engineering experience, and human capital, there are few, if any, key missile components that the country needs to acquire through foreign assistance or procurement. This makes the future development of North Korea’s missile capabilities less susceptible to external influence and therefore subject primarily to policy and strategy imperatives determined by North Korean officials.

Besides nuclear warheads and delivery vehicles, a state seeking to operationalize its nuclear arsenal requires a range of additional enabling capabilities. Little is known about the command, control, and communication (NC3) of North Korea’s nuclear forces, but its development of such NC3 systems presents real dilemmas. On the one hand, North Korea’s Kim Jong-un clearly wants to deliver a message to the outside world that he is in total control of nuclear weapons and therefore other countries should not overreact to unjustified concerns of incidental or unauthorized use of the weapons. In past statements, for example, Kim emphasized the importance of the “safe operation of [a] nuclear attack system” and “a unitary system of command and control over nuclear force.”¹⁷ On the other hand, facing an increasing threat of so-called decapitation operations from U.S. and South Korean forces, the North Korean leadership might have a strong incentive to delegate launch authority for nuclear weapons to operational-level military officials to ensure retaliation. North Korea’s NC3 dilemma will be further exacerbated if it deploys sea-based nuclear forces in the future. Compared with land-based missile forces, it is much harder to establish robust NC3 connections between the national command authority and ballistic missile submarines on patrols at sea.

In addition to securing effective command and control over nuclear weapons, North Korea is making efforts to improve its nuclear forces’ ability to execute missile strikes under battlefield conditions. For instance, reports in 2017 indicated that North Korea carried out trainings and exercises to prepare to conduct salvo launches of ballistic missiles against potential regional military targets.¹⁸

Capabilities that North Korea has developed to employ its nuclear weapons and integrate its nuclear forces into its overall military planning and operation have not been as widely analyzed in the analytic community but deserve additional careful examination.

Possible Future Nuclear Developments

Looking to the future, the specific nuclear capabilities North Korea will develop, test, and field should provide important indicators about its strategic objectives—beyond how it characterizes those objectives in official communications. If North Korea stays on its current trajectory, it will likely continue to invest in more survivable strategic nuclear weapons, such as solid-fueled ICBMs carried on transporter-erector-launchers, and to increase its arsenal of such missiles. But a 2017 U.S. Defense Department report assesses, for example, that North Korean activities and rhetoric may suggest it “seeks to achieve a capability that goes beyond minimal deterrence to one that could provide greater freedom of action for North Korean aggression or coercion against its neighbor.”¹⁹ It is quite possible after obtaining a sufficient strategic nuclear deterrent capability, North Korea could shift its focus to developing small-yield, short-range nuclear weapons that are more useful for offsetting conventional military imbalance on the battlefield. Close monitoring of such activity should yield a better understanding of North Korea’s strategic goals and trends in its military behavior. That said, as observed in other states with nuclear weapons programs, many other factors can influence the makeup and scope of a nuclear arsenal, such as technology advancements and competition among military services for a larger share of the nuclear mission.

In particular, considering possible North Korean employment of nuclear weapons, it is important to assess a broader range of factors that might influence its decisionmaking. For instance, if the gap in conventional military capabilities between North Korea and the U.S.-ROK and U.S.-Japan alliances continues to grow, or if North Korea perceives its nuclear assets to be at risk of a conventional preemptive attack, Pyongyang may threaten nuclear first use during a conventional conflict, even if it has a general interest in avoiding nuclear escalation. North Korea’s lack of strategic position in geographical terms is another important factor that might encourage early employment of nuclear weapons. Such non-nuclear factors need to be considered together with North Korea’s growing nuclear capabilities.

The opacity of North Korean strategic decisionmaking increases the likelihood that analysts, in particular those in different countries, may draw varying conclusions about North Korean intentions from the same information. Comments by officials from East Asian states suggest that divergent views exist on even basic issues such as North Korea’s nuclear and missile capabilities, let alone more complex questions about objectives and behavior. For example, Russian officials have presented much lower missile range assessments following some North Korean tests than those provided by the United States, South Korea, and Japan. And among Chinese and Russian security experts, there is also a sense that Western assessments of North Korea’s nuclear capabilities have been consistently exaggerated. In this regard, international expert dialogue could help prevent disagreements from undermining cooperative efforts in response to North Korea’s threatening behavior.

Forecasting North Korea’s Nuclear Objectives

North Korean statements and behavior over time suggest a series of potential overlapping external political and military aims.²⁰ Some of these (for example, international recognition) pose political challenges for Seoul and Washington, whereas others (for example, limited conventional military attacks backed by nuclear threats) create profound deterrence and reassurance problems for the U.S.-ROK alliance. Even if North Korea is less likely to attempt its riskiest or most challenging objectives, political discourse in the United States and South Korea demonstrates clearly that policymakers still worry about them.²¹ For instance, it is not uncommon to hear senior policymakers opine that North Korea intends to use nuclear weapons to fulfill its ultimate goal of reunifying the Korean Peninsula under its flag.²²

One of the most significant challenges in forecasting how North Korea might use its nuclear weapons is teasing apart the connections between objectives and weapons development activities. Applying evidence from one domain to support analysis in another is a speculative exercise and easily prone to mirror-imaging or other forms of bias. Below are a range of plausible, potential objectives based on North Korea’s past statements, actions, or other evidence—regardless of whether Pyongyang currently possesses the necessary and sufficient nuclear capabilities to achieve each objective. The objectives are listed according to ascending level of risk that North Korea’s actions would serve to escalate a provocation. (For the sake of simplicity, how North Korea’s reported chemical and biological weapons capabilities might factor into this equation is not considered, but most analysts recognize that these weapons also constitute a major element of North Korea’s deterrent threat.)

Deter Preventive or Preemptive Strikes

One of North Korea’s most explicit objectives in employing its nuclear arsenal would probably be to deter any U.S. preventive or preemptive strikes that might threaten regime survival. Since North Korea cannot deny the United States the ability to carry out such strikes, peacetime deterrence is based almost entirely on Pyongyang’s ability to deliver an unacceptable punishment in response. If the United States conducted preventive strikes, especially in support of regime change, North Korea could launch nuclear attacks against South Korea, Japan, and U.S. military forces stationed in the region, and possibly the United States itself.²³

However, North Korea does not seem to regard this objective as especially critical to its nuclear strategy since non-nuclear capabilities have long been the central pillar of its peacetime deterrence against U.S. or South Korean strikes. North Korea deploys a large number of long-range artillery and rocket forces in protected positions along the Military Demarcation Line. In many ways, these non-nuclear capabilities are more credible as a peacetime deterrent than North Korean nuclear forces.²⁴ Though North Korean nuclear use could invite nuclear retaliation from the United States and spell the end of the Kim regime (perhaps one of the few clear and consistent signals U.S. officials have communicated to North Korea over the years), non-nuclear punishment may not. In any case, North Korea’s nuclear capabilities certainly complicate U.S. planning for preventive or preemptive strikes (and diminish the already low probability that such attacks would be carried out), even if that is not North Korea’s primary objective.²⁵ North Korea’s peacetime deterrence is therefore likely to rely primarily on conventional forces, and nuclear forces will play a supplementary and largely psychological role.

Normalize Relations with the United States and Japan

North Korea has historically used its nuclear and missile capabilities as leverage to improve and ultimately seek to normalize diplomatic relations with the United States and Japan. The U.S.–North Korean Agreed Framework of 1994 included “formal assurances” against the threat or use of nuclear weapons by the United States. It also mandated that the United States and North Korea “move toward full normalization of political and economic relations.” The Six-Party Joint Statement adopted in 2005 affirmed that the United States had no intention to attack or invade North Korea with nuclear or conventional weapons and that the two countries would take steps to normalize their relations. It also included a provision for North Korea and Japan to take steps to normalize their relations.²⁶ Though none of these agreements reached fruition, they clearly demonstrate Pyongyang’s past willingness to leverage nuclear capabilities for improved relations, presumably with the ultimate hope of a peace treaty and security assurances. The details of the bargain changed with each negotiation, but all the agreements involved constraints on nuclear and missile activities and a promise of future denuclearization.

Will North Korea seek to bargain again now that it has a demonstrated weapons capability? Official North Korean statements make it clear that Pyongyang seeks recognition as a nuclear-armed state and treasures its nuclear weapons.²⁷ At the same time, North Korea’s development of improved nuclear and missile capabilities after the breakdown of the Six-Party Talks in 2008 could, in theory, provide greater bargaining leverage. For instance, it is plausible that North Korea could agree to negotiate an arrangement that caps the size and scope of its nuclear arsenal in return for improved relations and sanctions relief.²⁸ The most important question is whether a modus vivendi exists between two strongly held positions: North Korea’s intent to retain nuclear capability at all costs and the United States and its allies’ policy that denuclearization be the objective of negotiations.²⁹

Deter Responses to Low-Level Provocations

Possession of nuclear weapons could embolden North Korea to carry out more frequent, more lethal, or riskier low-level military provocations against U.S. and South Korean military forces. Such a scenario might emerge as a result of a “stability-instability paradox,” in which stability at the level of strategic deterrence decreases the probability for conflict escalation, which, in turn, encourages adversaries to undertake actions that lead to instability at the tactical and operational levels of warfare.³⁰ Though the United States is likely to take further steps to limit vulnerability to North Korean attacks, including by deploying more missile defense systems, North Korea’s ability to target the United States does create a new kind of mutual deterrence.³¹ In this circumstance, North Korea could feel confident that its nuclear weapons would restrain U.S. and South Korean retaliation options against any North Korean tactical provocations.³²

North Korea has a long history of such provocations, typically tied to a specific political, military, or diplomatic objective.³³ The most egregious of these acts—the attempted assassination of South Korean president Park Chung Hee in 1974 and the seizure of the USS Pueblo in 1968—occurred many decades ago. Since Kim began his rise to power in 2009, North Korean provocations have included sinking a South Korean Navy corvette, shelling a South Korean island in 2010,³⁴ and placing landmines along the path of a regular South Korean military patrol in the Demilitarized Zone in 2015. The specific objectives behind such actions remain opaque—whether they were to increase Kim’s domestic political prestige, provoke a crisis that forces diplomatic intervention by outside powers, or achieve specific military aims.

Since nuclear weapons increase the risks associated with conflict escalation from such provocations, North Korean leaders could be tempted to instigate low-level attacks to harass South Korea and keep U.S. and South Korean military forces on the defensive. This would place new stress on, and challenge the credibility of, South Korea’s proactive deterrence military posture, which aims to discourage North Korean attacks through a promise of manifold retaliation rather than a proportional response. It might also induce the United States to pressure South Korea not to escalate in retaliation, creating additional strain on th