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The Peninsula

South Korea’s Drive Toward Deterrent Capabilities

Published March 10, 2023
Author: Andy Hong
Category: South Korea

This piece is one of 12 contributions to KEI’s special project on South Korea’s nuclear armament debate that will run on The Peninsula blog over the next month. The project’s contributors include young, emerging, and mid-career voices, examining the debate from a historical, a domestic, and an international perspective. On Wednesday, March 15, KEI will host a conference featuring our various contributors’ work at our Washington, D.C. office and launch a compilation of all the pieces in a single, special KEI publication.

President Yoon Suk Yeol caused an immediate reaction in Washington, DC when he mentioned the possibility of an independent nuclear deterrent for South Korea. However, South Korea’s potential development of nuclear weapons is nothing new. Over half a century ago, Seoul initiated a project to develop nuclear weapons and nuclear-capable delivery systems. Although its effort to develop nuclear weapons was curtailed, South Korea has successfully developed and gradually advanced potential dual-capable delivery systems. Retracing these steps sheds light on the current debate.

The Warhead

South Korea’s first pursuit of an independent nuclear deterrent came at a time of great geostrategic uncertainty in the early 1970s. The United States was disengaging from Vietnam and Southeast Asia more broadly and, under the Nixon Doctrine, passing a greater defense burden to its allies. Meanwhile, the Sino-Soviet split and U.S.-Sino détente introduced new complex variables in Northeast Asian geopolitics. Seoul, which had committed the largest foreign troop contingent to Vietnam while confronting a major conventional threat from North Korea, now faced the withdrawal of one of the two remaining U.S. divisions from Korea.

Amidst uncertainty regarding the U.S. commitment, Park Chung-hee directed the Agency for Defense Development (ADD) in November 1971 to develop a nuclear deterrent as to counter Pyongyang’s superior conventional forces. The Korea Atomic Energy Research Institute (KAERI) assisted ADD in the acquisition and development of nuclear reprocessing and fuel fabrication infrastructure from abroad.

Importantly, South Korea had already begun nuclear research in 1956. In the process, Seoul had enthusiastically joined various nuclear treaty regimes to signal its peaceful intent and secure U.S. support—joining the IAEA in 1957, ratifying the Partial Test Ban Treaty in 1964, and signing the Nuclear Non-Proliferation Treaty (NPT) in 1968. However, by 1971, ROK research had expanded to other international partners, initially due to failed deals with the United States, to evade scrutiny from Washington. In May 1972, ROK nuclear technocrats secured an agreement with France to acquire nuclear reprocessing and fuel fabrication technology, critical for enriching nuclear materials to weapons grade.

By 1973, a special project team within KAERI was fully engaged in the mission to acquire an independent nuclear deterrent, using a budget of $1.5 to $2 billion for the development of a 20-kiloton plutonium device. KAERI ran a tight and secret network of actors from the Blue House and various ministries, while avoiding interaction with the Ministry of National Defense given its deep integration with the U.S. military. Two further breakthroughs advanced the project: interim contracts with French firms for fuel fabrication and spent-fuel reprocessing technology; and an agreement with Canada for a CANDU heavy water reactor. These were critical steps toward plutonium extraction for a 20-kiloton bomb. Ironically, Seoul finally ratified the NPT in 1975—7 years after signing it—as a precondition to acquire the CANDU reactor with proliferating intent.

Driven partly by India’s nuclear test in 1974, U.S. officials were increasingly attuned to the possibility of nuclear proliferation in the developing world. In the case of Seoul, Washington’s concerns were piqued  by a December 1974 telegram sent from the U.S. Embassy, Seoul. Subsequent U.S. pressure resulted in the cancellation of the French and Canadian contracts, putting an end to Seoul’s ambitions.

However, in 1977 with President Carter’s efforts to withdraw all U.S. ground forces from Korea, tensions flared again when KAERI’s fuel reprocessing efforts moved to the Korea Nuclear Fuel Development Institute (KNFDI) to quietly continue the project. But, increased U.S. scrutiny, strengthened IAEA safeguards, and Seoul’s 1975 ratification of the NPT once again foiled South Korea’s progress. By the time of Park’s demise in 1979, his enormously risky, decade-long gambit seemed to have also ended—after jeopardizing South Korea’s growing civilian nuclear sector, its alliance with the United States, and the security environment of Northeast Asia.

Nevertheless, the issue was once again thrust into the public light when in 2004, Seoul admitted to the IAEA that South Korean scientists had four years prior enriched a small amount of uranium to near-weapons grade. The revelation was quickly followed by a public probe, as well as skepticism that then-president Kim Dae-jung was directly involved in the secret project. Although the 2004 incident was  short-lived compared to the events in the 1970s, several key takeaways remain: South Korea had the capacity to develop enrichment technologies, (although the scale of such capacity remained unclear); any movement toward proliferation was perceived as immensely destabilizing by the United States and the international community, especially following Pyongyang’s withdrawal from the NPT; and the international response and condemnation would be unequivocal and swift.

Twenty years later, no such project has materialized yet public discussion on South Korea’s potential nuclear armament has reemerged. South Korea has one of the world’s most advanced civilian nuclear programs and is a major exporter of such technologies. Seoul today is critically linked to—and is one of the greatest beneficiaries of—the principle of the peaceful atom, cooperating with the IAEA and the Nuclear Suppliers Group (NSG) to contribute to global prosperity. South Korea is both deeply embedded in and a major stakeholder of civil nuclear power—highly dependent on the NSG for fissile material, and a beneficiary of lucrative nuclear exports. Beyond the technical difficulty in developing a nuclear weapons program, the consequent cutoff from NSG and U.S. action against ROK exports of nuclear technology would deal unavoidable and severe damage to South Korea’s nuclear industry and prestigious reputation in the sector.

The Triad

South Korea’s conventional weapons advancements are also a critical variable in Seoul’s potential development of an indigenous nuclear deterrent. While not necessarily designed with nuclear capabilities in mind, the ROK military is well on its way to developing latency for an independent nuclear triad: free-fall and air-launched ordnance, land-based ballistic missiles, and submarine-launched missiles.

Starting in the 1970s, the free fall and air-launched delivery component was perhaps the most readily available. South Korea initially received then-state of the art F-4D aircraft as a concession for Seoul’s involvement in the Vietnam conflict, and later purchased the upgraded F-4E for the modernization of the rapidly aging Republic of Korea Air Force (ROKAF). The acquisition of such U.S. designs alongside the attempted development of a nuclear device, provided for potential aerial deployment of nuclear weapons. The ROKAF has since added many more advanced U.S. airframes to eventually replace the aging F-4s and augment the growing indigenous fleet—from the F-16C/D (first delivered 1986), to the F-15K (2005), and the F-35A (2019); all nuclear-capable designs.

Beyond possession of an airframe, the air-deployed ordnance with which to deploy any nuclear warhead still poses a challenge for ROKAF. Rather than depend on American airframes, South Korea may enhance its latency on the air-dropped component with its concurrent development of the KAI KF-21 Boramae and DAPA’s Korea Long-Ranged Air-Launched Cruise Missile (ALCM). Domestically procuring both platforms preempts the burdensome regulatory requirements that come with imported weapons. Based on a Swedish-German design, the ALCM (for which the venerable Phantom serves as a test bed) is unlikely to itself mount a nuclear warhead; nevertheless, the experience could give South Korea the knowhow and industrial infrastructure to build similar air-launched weapons that could be nuclear-capable.

The land- and submarine-launched ballistic missile arms of the South Korean military form a storied yet more recent development. Like the nuclear warhead it would later be envisioned to carry, South Korea’s ballistic missile program also came from a clandestine ADD project under direction of the Blue House in 1971. The project began with an agreement with McDonnell Douglas to jointly research modifications to the Nike Hercules surface-to-air missile, with limits on range and payload to 180 kilometers and 500 kilograms, respectively. Despite resistance from the U.S. Department of State, the project accelerated in 1975 under the Yulgok Plan to close the capability gap with Pyongyang. In 1978, Seoul successfully demonstrated the Baekgom surface-to-surface ballistic missile. In 1979, with sustained U.S. pressure on the now well-known nuclear program, the Park regime codified the initial range and payload limitations of 180 kilometers and 500 kilograms. Following Park’s assassination in the same year, his successor Chun Do-hwan continued to observe the limitation with the Hyunmoo missiles. It is of note that nevertheless by 1990, U.S. inspections found that Hyunmoo retained the potential to extend its range to 250 kilometers—demonstrating Seoul’s willingness to stretch the boundaries of its potential lethality.

As U.S. resistance held against Seoul’s calls for renegotiating the missile guidelines, Seoul turned to the newly formed Russian Federation through the Bulgom (Siberian Bear) Operation. The technology exchange of platforms and knowhow with Russia not only accelerated development of South Korea’s military missile capabilities, but also formed the foundation of South Korea’s space program. In 1997, Seoul eventually succeeded in setting new ballistic missile guidelines to 300-kilometer range and 500-kilogram payloads, and joined the Missile Technology Control Regime (MTCR)—despite initial U.S. opposition and the imposition of several conditions calling for transparency from Seoul. With subsequently growing North Korean nuclear and rocket technology, the guidelines were again renegotiated in 2012 to a range that covers 800 kilometers. Demonstrating South Korea’s latent capabilities, it only took two years for Seoul to develop a ballistic missile with a range of 500 kilometers. Two more revisions have taken place: in 2017, all restrictions on payload weight were lifted, and in 2020, Seoul received the green light to develop solid-propellant rockets—a landmark development, as liquid-fuel rockets require laborious and time-consuming fueling directly prior to launch, whereas solid-fuel rockets are shelf-stable and can be launched more quickly.

By the May 2021 U.S.-ROK summit, all remaining restrictions were effectively removed. Development had already been proceeding at a breakneck pace. In March 2020, DAPA announced that the Hyunmoo-4 could successfully deliver a 2,000 kilogram payload over 800 kilometers. In September 2021, South Korea became the first nation without nuclear weapons to have SLBM capabilities, also breaking the 1979 restrictions by over 200 kilometers. Most recently in December 2022, Seoul belatedly announced the successful test of a solid-propellant space launch vehicle just six months after the second-ever successful launch of the older, liquid-fuel Nuri.

Nevertheless, South Korea faces resistance on its long-range strike capabilities. In the 30 years since the ROK Navy (ROKN) commissioned the first submarine in South Korean history, South Korea has taken great efforts towards rapidly advancing its submarine-based strike capabilities. However, its capabilities still fall short of nuclear propulsion that can allow submarines to move faster and remain submerged for longer. A ballistic missile submarine’s ability to remain undetected and constantly moving provides an immense deterrent capability; a capability provided by nuclear propulsion. South Korea has been pushing for a Korean nuclear submarine (KSSN) publicly for nearly twenty years. The U.S. agreement to transfer nuclear submarine technology to Australia with AUKUS only galvanized the debate.

Whether assistance from the United States or France, or independent South Korean development of miniature reactors opens the doors to KSSN is still uncertain. However, AUKUS and renewed calls for Seoul to proceed with KSSN is indeed reminiscent of the broader South Korean ballistic missile story. It is a story of constantly shifting boundaries: from initial restriction and resistance to conditional allowance, and to eventual unrestricted development. As a result, Seoul may foresee a future in which the restrictions on nuclear devices proceed in much the same way as they were lifted for its missile capabilities. While it may seem that tectonic shifts are underway in Indo-Pacific security, for Seoul to arrive at such a conclusion remains misguided and reductionist: a nuclear device involves a host of far more complex variables such as technical dependency on the nuclear supplier group, formal international legal ramifications with regards to the NPT, and customary international obligations to nonproliferation.

The Doctrine (or Lack Thereof)

Nuclear weapons, like many instruments of war and peace, cannot fully achieve their stated goals in the absence of a thoroughly developed doctrinal infrastructure and rigorously trained plan of employment. There has been very little discussion on the actual doctrine of nuclear use in South Korea, nor is there an infrastructure in place to help direct and sustain a nuclear force.

In the 1970s, it was simply conceived that an indigenous nuclear weapon would be deployed either on U.S.-built combat aircraft or on the Baekgom missile—even though the procurement and upkeep of both assets depended on U.S. approval. The institutional structure of the South Korean military even today preempts the development of such plans, as the ROK military falls under the wartime operational control of Combined Forces Command. As long as the United States remains committed to nonproliferation, even conducting joint nuclear exercises with U.S. assets remains tenuous at best.

Some indicators suggest Seoul is seeking to amend this institutional impasse. President Yoon’s goals to establish a South Korean Strategic Forces Command by 2024 could potentially be a step in this direction, as the aforementioned triad would fall under the SFC. The SFC also would play a key role in the Kill Chain strategy and Korea Massive Punishment Retaliation plan, which for the comprise Seoul’s conventional deterrent against Pyongyang.

However, a preemptive or retaliatory strategy does not alone cover the myriad implications of developing nuclear deterrent capabilities. The ROK military has done exercises for chemical, biological, radiological, nuclear, and explosive (CBRNE) environments, often in conjunction with U.S. forces. Conventional equipment has also been upgraded to withstand CBRNE environments. However,  at the height of the last bout of escalation in 2017, it was found that South Korean civilian shelters and bunkers were in a woeful state. The civilian infrastructure required for nuclear deterrence is severely lacking, with many shelters in disrepair, even fewer being suitable for nuclear war, and extremely low public readiness. To discuss the development and deployment of nuclear weapons without concurrently discussing how to prepare the civilian population—or whether preparation is possible at all—for nuclear war is a distressing oversight that points to the lack of depth in the public discourse today.

South Korea’s tortuous, fifty-year drive toward deterrent capabilities offers clarity as to just how complex the issue is. The interplay of security threats and guarantees, of technological potential yet infrastructural neglect, demonstrates the difficulty of relegating the monstrous magnitude of nuclear armament to a simple yes or no question. On one hand, it is necessary to realize that it has always been difficult, if not more so today, for South Korea to seriously move forward with an indigenous nuclear program both on political and technical grounds. On the other hand, one must recognize that today’s debate is another point in a half-century endeavor.

Andy Hong is a Program Officer with the Korea Economic Institute of America. The views expressed here are the author’s alone.

Photo from Shutterstock.

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