On June 6, South Korea and the United States test-fired eight ballistic missiles, a day after North Korea test-fired eight of its own ballistic missiles, offering a snapshot of an arms race that has been going on for some time. Since 2019, North Korea has resumed testing its missiles, including intercontinental ballistic missiles it tested earlier this year, lifting its 2017 self-imposed moratorium on nuclear weapons and missile tests. Just during the first half of 2022, it has test-fired over 30 missiles, breaking its 2019 record of 25. A seventh nuclear test seems imminent judging from recent activities at North Korea’s Punggye-ri nuclear testing site. After Kim Jong Un defended his acceleration of the arms buildup at a meeting of the Central Committee of the Workers’ Party of Korea last week, North Korea’s provocations will likely continue. South Korea, for its part, is also accelerating its military buildup, seeking more sophisticated ballistic missiles, including submarine-launched ballistic missiles and hypersonic cruise missiles, as well as missile defense systems. The country’s new president, Yoon Suk-yeol, has vowed to construct a powerful military.
Driving the arms race on the Korean Peninsula is what I call a “double asymmetry of power”: an asymmetry at both the nuclear and conventional levels. North Korea is enhancing its nuclear and missile capabilities in order to secure a survivable nuclear arsenal vis-à-vis the United States. Lacking a nuclear option, South Korea is seeking to counter North Korea’s nuclear threats with sophisticated conventional capabilities. Lagging far behind South Korea in terms of conventional capabilities, North Korea is seeking to modernize its conventional weapons, as well. Due to the power imbalance at both the nuclear and conventional levels, and the difficulty in assessing the power balance across the conventional and nuclear domains, neither country is likely to feel assured of its security, and thus will continue to enhance its military capabilities to deter the other side’s threats.
The North’s March Toward a Survivable Nuclear Arsenal
North Korea is advancing its nuclear and missile capabilities to deter the United States. It is believed that North Korea has not yet acquired the ability to launch a nuclear attack against the United States in light of North Korea’s 2017 ICBM test that failed on the reentry phase. The re-entry vehicle technology protects a nuclear warhead from the intense heat and vibrations generated when a long-range missile re-enters the Earth’s atmosphere. One of the three missiles North Korea launched on May 25 seems to have been aimed at testing its re-entry vehicle technology (this missile had a flight path described as a “double arc” with the missile ascending and descending twice, which may indicate a re-entry vehicle breaking off from the missile.) In addition, North Korea needs to enhance its second-strike capability: the ability to retaliate with nuclear weapons against a nuclear attack. Its recent test of the Hwasong 17 missile may be aimed at filling this gap. Much attention has been paid to the size of the Hwasong 17 — it is the largest ICBM ever developed (hence the name, “monster missile”). The size matters because the missile can carry a large payload, potentially including multiple re-entry vehicles, which complicates a missile-defense system’s job of shooting down all of them at once. The fact that the missile was tested from a mobile launcher makes it even more difficult for missile-defense systems to target. North Korea’s recent testing of a submarine-launched ballistic missile and hypersonic glide vehicles could also pose threats to missile-defense systems. All of these are aimed at enhancing North Korea’s second-strike capability.
A Nuclear Option for the South?
To counter North Korea’s nuclear threats, South Korea has relied on extended deterrence from the American nuclear umbrella. The credibility of extended deterrence, however, has been questioned time and again, and is further undermined now that North Korea is inching closer to acquiring the capability to launch a nuclear attack against the United States and securing a second-strike capability. If North Korea can pose direct nuclear threats to the United States, defending South Korea may become too costly for the United States.
Due to this uncertainty, South Korea is looking at ways to develop its own capability to counter North Korea’s nuclear threats. The most effective way to balance nuclear capabilities would of course be to develop its own such weapons. According to a recent Chicago Council survey that my colleagues and I conducted, 71 percent of South Koreans supported nuclear armament. The public overwhelmingly preferred an independent arsenal (67 percent) over hosting a deployment of U.S. nuclear weapons (9 percent). The South Korean public’s support for nuclear weapons, especially their indigenous development, is robust.
Of course, we should distinguish what the public wants from what leaders can do. In reality, it is highly unlikely that Seoul will go nuclear, because the costs outweigh the benefits. Should South Korea decide to develop its own nuclear weapons, the United States would likely withdraw its security guarantee. Although South Korea has advanced nuclear technologies, it lacks the fissile material production capability, and Seoul would still need three to five years to acquire a workable nuclear arsenal. During this period, South Korea would be critically vulnerable to North Korea’s nuclear threats. That is to say, in the short term, South Korea’s nuclear armament would decrease rather than increase its security. Also, it’s likely that damage to South Korea’s export-dependent economy in the form of sanctions would be significant. Sanctions against South Korea imposed by China alone in the wake of the deployment of the American Terminal High Altitude Area Defense system were severe enough. The prospect of facing large-scale multilateral economic sanctions is likely to erode support for nuclear armament, when it comes down to it.
Given the enormous security and economic costs associated with nuclear armament, another option for South Korea is nuclear hedging: maintaining a viable option for the relatively rapid acquisition of nuclear weapons but stopping short of their development. Though it’s hard to prove, President Moon Jae-in seems to have pursued such an option by preparing to build nuclear-powered submarines, ostensibly to counter North Korea’s submarine-launched ballistic missile capability. But this could in fact have been to acquire the ability to produce nuclear fissile materials as fuel for submarines — fuel that could later be converted into nuclear weapons. Combined with the country’s ballistic missile program, this would make it possible for South Korea to acquire a workable nuclear arsenal in short order.
However, Washington remains against South Korea’s development of nuclear-powered submarines. Seoul has been trying to acquire U.S. consent but hasn’t been successful. The nuclear cooperation agreement between the United States and South Korea prohibits the latter’s use of nuclear technology for military purposes. As such, nuclear hedging is not yet feasible.
South Korea’s Conventional Deterrence: Will This Really Work?
Given the uncertainty of extended deterrence and the lack of a viable nuclear option of its own, South Korea is, for now, pursuing the so-called three-pronged defense strategy of conventional deterrence to counter the North’s nuclear threats. It consists of the Kill Chain strategy (preemptive strikes against North Korean nuclear missiles prior to launch), the Korean Aerial Missile Defense system, and the Korean Massive Punishment and Retaliation strategy (in essence a decapitation strategy aimed at taking out the North Korean leadership). Moon described it in watered-down terms, such as “strategic strike system,” in order not to provoke Pyongyang, but Yoon recently reinstated the original names.
In order for conventional deterrence to work, it must convince Pyongyang of the prospect of its success. For that, South Korea needs a larger and more capable arsenal of conventional assets. For Kill Chain, South Korea is developing cruise missiles with high precision as well as intelligence, surveillance, and reconnaissance assets that enable detection of North Korea’s nuclear and missile activities. South Korea is enhancing its missile defense capabilities by developing its indigenous assets as well as purchasing more American ones. For the decapitation strategy, South Korea requires ballistic missiles, bunker busters, and high-explosive shells, with which it can strike potential North Korean elites’ hideouts as soon as Pyongyang demonstrates its intention to use a nuclear weapon.
Deterring nuclear use with conventional weapons is challenging, however. The third prong, the decapitation strategy, has the best chance of deterring, although it’s still not a sure thing. Given that North Korea’s center of gravity is its leadership, taking out the country’s leaders would inflict unacceptable harm, in which case the logic of deterrence would hold. Indeed, Pyongyang has taken South Korea’s decapitation strategy seriously. For some time, it has sought to acquire South Korea’s operational plans for decapitation, and just last month, the South Korean media reported that a South Korean army captain transferred part of the plan to a North Korean operative. On the other hand, the effectiveness of Kill Chain is questionable. Even with enhanced surveillance capabilities, detecting and tracking North Korean missiles is difficult given the North’s ability to launch missiles from submarines and road-mobile launchers. Even if detection is feasible, it would be challenging for Seoul to strike North Korea’s missile launchers and command and control within a short time frame. The utility of missile defense is also dubious in light of North Korea’s development of hypersonic and multiple re-entry vehicles. Hence, understandably, skepticism abounds whether Seoul can ever deter nuclear threats with conventional weapons.
Nonetheless, Seoul cannot simply rely on America’s extended deterrence without exploring deterrence of its own. South Korea will likely seek to make its conventional deterrence as credible as possible, even if it may never be truly able to counter threats posed by North Korea’s nuclear arsenal.
Nukes May Not Be Enough: North Korea’s Conventional Modernization
North Korea, for its part, is seeking to enhance its own conventional capabilities in response to South Korea doing so. Nuclear weapons are not a cure-all — they do not necessarily eliminate all security threats, and conventional capabilities are still important in countering low-level confrontations. North Korea’s conventional capabilities significantly lag behind those of South Korea. Much of its conventional weapons are outmoded, and its soldiers are malnourished. North Korea’s defense spending is far lower than South Korea’s. To put things into perspective, South Korea’s 2020 defense budget was $45.7 billion, about 1.5 times North Korea’s entire GDP that year, which was $27.4 billion. Plus, a large portion of North Korea’s defense budget goes into its nuclear and missile programs. Therefore, North Korea is seeking to close the gap in conventional power. On the 75th anniversary of the founding of the Workers’ Party of Korea in October 2021, North Korea displayed new or updated conventional weapons, including multiple-launch rocket systems, short-range ballistic missiles, air-defense radar vehicles, anti-tank missiles, and smoke grenade launchers. Still, North Korea has a long way to go to catch up with the South.
Under these conditions of double asymmetry, a continued, unabated arms race on the Korean Peninsula is a near-certainty. South Korea won’t be confident that its conventional weapons will ever be enough to deter North Korea’s nuclear threats, while North Korea will continue to feel vulnerable not only to the American nuclear umbrella, but also to the South’s far superior conventional capabilities. Unlike arms races in a single domain where parity can be measured with relative confidence and the adversaries can reach a new equilibrium, double asymmetry makes it hard for either side to feel confident their military might will have a deterrent effect on the other. For this reason, the current situation on the Korean Peninsula may be arguably even more precarious and persistent than an arms race between nuclear powers.
What does this mean for U.S. policy? Unfortunately, Washington does not seem to have any good options to alleviate the pressures at play in the arms race. Denuclearizing North Korea has been tried and failed. At this point, an arms-control deal with North Korea seems like a more feasible goal, but signing one would make Seoul feel more insecure and accelerate its military buildup even further. Washington can assure South Korea of America’s security guarantee only so much, but not enough for Seoul to renounce the path forward to developing autonomous self-defense.
Lami Kim is an assistant professor and director of Asian Studies Program at the U.S. Army War College and a U.S.-Korea NextGen Scholar at Center for Strategic and International Studies. This piece is based on her presentation at the Norwegian Institute of International Affairs. The views expressed are those of the author and do not necessarily reflect the official policy of the U.S. government.