South Korea’s Conventional Forces Buildup: The Search for Strategic Stability

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How should South Korea respond to North Korea’s growing arsenal of nuclear-tipped missiles? Some argue that Seoul should improve its conventional capabilities in order to deter Pyongyang’s nuclear adventurism and achieve stability on the Korean Peninsula. Others contend that a South Korean arms buildup in response to North Korea’s nuclear developments could result in inadvertent crisis escalation.

In their recent essays in War on the Rocks and International Security, Ian Bowers and Henrik Hiim rightly point out that South Korea’s conventional military forces are of growing significance for strategic stability with North Korea. However, they also argue that South Korea’s conventional forces are adding to the instability on the Peninsula. Bowers and Hiim conclude that “if the United States wants to ensure that any denuclearization initiatives are successful, it may need to persuade South Korea to undertake conventional arms reductions, particularly with regard to offensive capabilities.”



We respectfully disagree. South Korean conventional forces play a positive and even essential role in an alliance context with the United States in maintaining stability as North Korea nuclearizes. Our perspectives on this matter are informed by our experience as South Korean military officers involved in the development of deterrence theories and policies for the U.S.-South Korea alliance. We argue that South Korea’s conventional capabilities actually strengthen stability on the Korean Peninsula by reducing North Korea’s expectations regarding the utility of its nuclear weapons. As a result, the development of these conventional forces — in cooperation with its allies in Washington — helps Seoul prevent Pyongyang from achieving its strategic goals through nuclear adventurism.

South Korea’s Approaches to Deterrence

South Korea’s conventional capabilities have been designed to play a central role in establishing the U.S.-South Korean alliance’s deterrence posture and implementing a combined counter nuclear strategy. This approach is codified in the “tailored deterrence” strategy announced in 2013. This strategy is attuned to the specific characteristics of North Korea’s nuclear program. Specifically, it is based on the understanding that Kim Jong Un alone has the authority to employ North Korea’s nuclear weapons, that mobile missile launchers are the primary means of delivery, and that North Korea’s missiles are located in deeply buried tunnels. These features could permit the U.S.-South Korean alliance to spot early warning signs of nuclear attacks as well as to destroy the missiles during the stages of deployment and launch preparation. The strategy is based on both the U.S. commitment to extended nuclear deterrence and South Korea’s expected construction of conventional forces, as well as the interoperability of those forces with U.S. military assets.

South Korea’s conventional military capabilities with regard to deterring North Korea’s nuclear threats consist of three key elements: the Korea Air and Missile Defense system, the Kill Chain system, and the Korea Massive Punishment and Retaliation system. The Korea Air and Missile Defense system is a largely indigenous, layered missile defense system. Although it is still mostly conceptual and many components of the missile defense system are in the development stage, the South Korean military aims to establish early warning, command and control, and multiple intercept systems by the mid-2020s through steady investment. The Kill Chain system — run by the army, navy, and air force — consists of sensors, ground/sea-based ballistic and cruise missiles, and various precision-guided bombs. It attempts to detect imminent North Korean missile attacks and allow South Korean forces to destroy the country’s missiles and launchers preemptively. Lastly, the Korea Massive Punishment and Retaliation system involves the use of multiple kinetic and non-kinetic capabilities, including ballistic and cruise missiles, guided bombs, blackout bombs, and electromagnetic pulse weapons, to target North Korea’s leadership facilities following any nuclear attack. In fact, the Kill Chain system and the Korea Massive Punishment and Retaliation system share the same weapon platforms, although their approaches to using the available means differ. This represents one reason behind South Korea’s decision to integrate the Kill Chain system and the Korea Massive Punishment and Retaliation system in 2019 and expand the concepts into the Strategic Strike system to facilitate the efficient management of force buildup projects.

South Korea’s conventional capabilities reinforce deterrence on the Korean Peninsula. On the one hand, the Kill Chain system and the Korea Air and Missile Defense system both represent means of achieving deterrence by denial, as South Korea’s missiles are capable of striking North Korea’s missiles and launchers if attacks are imminent. On the other hand, the Korea Massive Punishment and Retaliation system aims to achieve deterrence by punishment. It is designed to convey the message that if North Korea chooses to use its nuclear weapons, then all the participants in the decision-making process, including Kim Jong Un, will be removed. Thus, the Korea Massive Punishment and Retaliation system is closer to a counter-force or counter-leadership strategy rather than a counter-value strategy.

Anticipating Concerns Regarding South Korea’s Conventional Forces

While South Korea believes that its conventional forces are key to stabilizing the military balance with North Korea, other analysts are concerned that South Korea’s moves will have the opposite effect. Bowers and Hiim, for instance, are concerned about increasing the risk of North Korea’s nuclear use, threatening strategic stability on the Korean Peninsula, and strengthening North Korea’s incentive to possess nuclear weapons.

The first concern is that if South Korea’s conventional forces are operated unilaterally and preemptively, it could increase the risk of North Korea’s use of nuclear weapons. While this concern is understandable, South Korea has no incentive to operate its conventional forces independently, unilaterally, or without any consultation with the United States. Additionally, given the various socio-economic factors involved, a preemptive strike that risks nuclear retaliation would impose nearly unimaginable costs on South Korea, which is democratic with an open economy. Therefore, the concern that South Korea’s enhanced conventional capabilities increase the risk of North Korea’s use of nuclear weapons is overstated.

The second concern is that South Korea’s conventional forces buildup might threaten strategic stability on the Korean Peninsula. The concept of strategic stability involves two essential conditions: arms race stability, which indicates that neither side has an incentive to rapidly engage in military buildup; and crisis stability, which implies that there is no incentive for either party to use military force first. If an arms race always results in an unstoppable crisis escalation, the point raised by the skeptics might seem reasonable. In practice, however, this is not always true. For example, if a strategic balance and mutual vulnerability are achieved following one side’s arms buildup, then both sides could lose the first-attack incentive. South Korea’s missile defense system and assured ability to retaliate would enable the U.S.-South Korean alliance to respond promptly and credibly to North Korea’s nuclear adventurism and so discourage Pyongyang from escalating a crisis by launching its preemptive and surprise attacks, thereby achieving strategic stability.

The third concern is that South Korea’s buildup of conventional forces could make it more difficult to convince North Korea to denuclearize via negotiations. In other words, even if the Biden administration succeeds in persuading Pyongyang that the United States does not pose an existential threat to North Korea, South Korea’s conventional forces represent an incentive for North Korea to preserve its nuclear weapons. This notion seems to hinge on the premise that if South Korea takes steps to disarm itself, North Korea might be more amenable to giving up its nuclear weapons. However, unilateral disarmament measures are unacceptably risky with an opponent as malicious and unreliable as North Korea. It is more likely that if South Korea scaled back conventional force modernization plans, North Korea would opt to use a coercive strategy against South Korea or even attempt to alter the status quo based on its newfound asymmetric military advantage. Such a situation would be an intolerable outcome for South Korea and the United States.

South Korean military restraint would not persuade North Korea to engage in negotiations to denuclearize. On the contrary, improving its conventional forces could actually give South Korea a negotiating advantage. South Korea’s counter-nuclear and counter-leadership capabilities are potential chips to be traded away if North Korea were willing to trade for reductions in its nuclear weapons or the size of the Korean People’s Army. Any unilateral arms reduction by Seoul will be a waste of a potential swap. Even if North Korea were to eliminate its nuclear weapons, it would still have a massive conventional military, including over one million soldiers, mechanized corps, and artillery divisions. South Korea has sufficient reasons to maintain its conventional capabilities to achieve deterrence and stability after denuclearization.

Conventional Deterrence Against North Korea

As North Korea’s nuclear capabilities improve, the most important issue for South Korea and its American allies is determining how best to deter Pyongyang from employing its nuclear weapons. During the Eighth Congress of the Korean Workers’ Party, Kim Jong Un revealed his intentions to separate South Korea from the United States and to reunify the Korean Peninsula under socialist rule. He plans on doing so, in part, by placing pressure on the alliance through the use of coercive nuclear threats.

South Korea and the United States should work together to convince North Korea that its nuclear threats will never succeed. To date, South Korea has relied on America’s nuclear forces to deter North Korea. However, as Brad Roberts notes, North Korea would more likely apply “gray zone” tactics — that is, military provocations backed by its nuclear weapons that fall below the U.S. nuclear threshold. If there is no means of bridging the gap between conventional and nuclear capabilities, North Korea would likely consider threatening to use nuclear weapons in a more aggressive manner, as it may mistakenly perceive that the United States would not intervene in a crisis on the Korean Peninsula. South Korea’s credible conventional threat, therefore, raises the expected costs of North Korea’s nuclear provocations and reduces the possibility of it achieving the desired political and military goals through the use of nuclear weapons.

Looking Ahead

South Korea’s conventional forces play a positive role in maintaining stability on the Korean Peninsula. Through providing flexible and credible options for deterrence, South Korea’s conventional forces prevent North Korea from making a strategic miscalculation and incorrectly determining that nuclear employment will bring about political benefits. Thus, the country’s conventional forces are essential in maintaining strategic stability through crisis management.

Proposals to reduce South Korea’s conventional capabilities in the hope of securing North Korea’s voluntary denuclearization are understandable given the dangers of conflict on the Korean Peninsula. Ultimately, however, unilateral South Korean restraint would not advance the security interests of South Korea or the United States. Instead, Seoul and Washington should work together to reinforce South Korea’s conventional posture. Doing so might even provide North Korea with incentives to return to the negotiating table and refrain from making nuclear threats. Moreover, it is time to think more seriously about how countries (e.g., Australia, Japan, the European Union, the United Kingdom, etc.) that share values with both the United States and South Korea could act collectively to prevent North Korea’s nuclear adventurism and help guarantee strategic stability on the Korean Peninsula.



Maj. Manseok Lee is currently a Ph.D. candidate at the University of California, Berkeley. Previously, he was a research associate at the Center for Global Security Research in the Lawrence Livermore National Laboratory. He has written multiple research articles concerning North Korea’s nuclear strategy, nuclear non-proliferation, and impact of emerging technologies on strategic stability.

Col. Hyeongpil Ham received his Ph.D. from the Massachusetts Institute of Technology. He has worked for more than 30 years at South Korea’s Ministry of National Defense, Ministry of Foreign Affairs, and Korea Institute for Defense Analyses. He led the governmental task force responsible for addressing North Korea’s nuclear threats and developing South Korea’s deterrence and defense strategy. 

The authors are especially grateful to Brad Roberts and a War On The Rocks subject matter expert for insightful comments on earlier drafts of this article. All statements of fact, opinion, or analysis expressed are those of the authors and do not reflect the official positions or views of the South Korean government and army.

Image: Wikicommons (Photo by Teukwonjae707)