South Korean Grand Strategy

Dr Christoph Bluth is Professor of International Relations at the University of Bradford

South Korea, in the 21st century, is facing a complex security environment as one of the few liberal democratic states persistently threatened by its neighbour and, therefore, a frontline state in the the emerging geopolitical configuration of the region. The persistent conflict between the Democratic People’s Republic of Korea (North Korea) and the Republic of Korea (South Korea) was, in part, a consequence of post-Second World War ideological divisions that developed into the Cold War. A dividing line between North and South Korea (since 1953: the demilitarised zone) was also a border between East and West. As a consequence, the scope for developing any kind of inter-Korean relationship was limited. At the same time, the embedding of the two Koreas on the different sides of the Cold War was also a stabilising factor as both Koreas enjoyed external security guarantees, and the United States had nuclear weapons deployed on the Korean peninsula to reinforce extended deterrence. The contemporary international system generally keeps the risk of armed conflict between states low except in some specific crisis regions such as South Asia or the Korean peninsula.

During the Cold War, nuclear weapons were central to the conflict between the Soviet Union/Warsaw Pact and the United States/NATO. They were also the dominant factor in the military balance, involving a substantial strategic nuclear arsenal and the triad of international range delivery vehicles, preparations for large-scale conventional conflict in Europe supported by tactical nuclear forces and proxy conflicts out-of-area. Although the United States and Russia still maintain substantial strategic nuclear forces, their role has changed fundamentally. As the prospect of large-scale warfare in Europe retreated, the United States developed effective global power projection capabilities based on conventional weapons. In contrast, Russia’s conventional military capacity shrunk to the point that nuclear weapons were considered essential as a deterrent of last resort, as well as Russia’s only claim to be a Great Power. However, since Russia launched its war of aggression on Ukraine, the role of nuclear weapons in the increasing tension between the Great Powers needs to be re-examined. The Ukraine War has also resulted in the development of a strategic axis between North Korea and Russia, as North Korea is assisting Russia in replenishing stocks of artillery munitions and ballistic missiles. This may involve cooperation on missile development that will enable North Korea to develop and deploy intercontinental ballistic missiles.

The first decade after the Cold War seemed to confirm the view that the military contingencies that the nuclear powers are likely to face do not involve nuclear weapons either as a deterrent or as a useful military tool. Indeed for the first time in their history the countries of Western and Central Europe did not face an external enemy. For example, in the conflicts in the Balkans four nuclear powers were engaged with their armed forces, but the possession of nuclear weapons had no relevance to their conduct or the course of the conflict. As very few states faced an external threat that would compel them to acquire nuclear weapons, all non-nuclear states joined the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). The conflict on the Korean peninsula and the emerging nuclear threat appeared to be an outlier in the overall global security landscape.

The changing strategic environment on the Korean peninsula

The strategic environment is changing in a way that reduces the credibility of extended deterrence. North Korea began 2023 as it ended 2022 – with some characteristic sabre-rattling in the form of missile tests. Having launched more missiles in 2022 than in any other year, on the morning of January 1 last year, North Korea tested a new multiple-launch rocket system. According to Supreme Leader Kim Jong-un, this new missile system could strike any part of South Korea with tactical nuclear warheads.

On the same day, Kim called for the North to “exponentially increase” its stock of nuclear weapons. There was a substantial reshuffle at the top of the military including the dismissal of Kim’s number two, Pak Jong-chon, who was replaced by the chief of the general staff, Rim Kwang- il, in an effort to push the military harder to achieve greater readiness and combat capability. Late last year, displays of belligerence by Pyongyang prompted a swift reaction from Seoul. After five drones penetrated South Korean airspace (one violating the no-fly zone over the presidential office in Seoul) the South Korean president, Yoon Suk-yeol, issued the military with a reprimand for not shooting them down and ordered a review of the 2018 Comprehensive Military Agreement with North Korea. The agreement established air, land and sea buffer zones to reduce the risks of armed conflict. Repeated violations of the agreement have led to speculation that Seoul could cancel the deal. Meanwhile, analysts in both Seoul and Washington are watching developments in Pyongyang carefully especially following Kim’s decision in September of 2023 to update legislation which now mandates an “automatic and immediate” nuclear response, putting security on the peninsula on a knife-edge.

Some analysts believe that this decision was a response to Yoon’s statement last year in the run-up to the March election that South Korea should consider pre-emptive strikes against the North’s command-and-control systems. South Korea has the capability to destroy North Korea’s leadership using precision guidance missiles and high-level reconnaissance facilities.

While this is said to be a retaliatory “kill chain”, it could in principle also be used pre-emptively, a strategy that Yoon championed during his 2022 election campaign. This was subsequently underlined when, in May last year, he took US president Joe Biden on a visit to the “kill chain command centre”.

On the Korean peninsula, the distances involved are relatively short – the South Korean capital Seoul, for example, is only 23km south of the border with North Korea. Early warning against a surprise missile attack is practically non-existent raising the risk of pre-emptive strikes. Yoon has declared North Korean denuclearisation to be the minimum requirement for the South to engage with the North economically and on security.

On August 15 last year – South Korea’s Liberation Day – Yoon made an offer with incentives for the North to denuclearise in return for what he called “an audacious plan that will vastly strengthen North Korea’s economy and improve the quality of life for its people”. Seoul’s principal concern is North Korea’s recent “more hostile and aggressive provocations based on confidence over its nuclear and missile capabilities”. The Yoon government redesignated North Korea as “the enemy” in a national defence white paper released earlier this year.

The reliability of the US-ROK alliance and South Korea’s nuclear dilemma

During the Trump administration, conflict over the cost of US forces based in South Korea and the missile defence system Thaad created severe tensions in Washington’s alliance with Seoul, leading to doubts about the reliability of the US nuclear guarantee. Biden has restored some level of confidence but he is a well-known advocate of nuclear arms control and “no first use” of nuclear weapons and has refused to advocate for nuclear deterrence over conventional threats. This is why Yoon and his foreign minister, Park Jin, attempted to get Biden to highlight the US commitment to nuclear deterrence without success.

As the Trump administration cast doubt over the reliability of the US-ROK alliance, conservatives in South Korea were increasingly voicing the need for South Korea to develop its own nuclear weapons to counter North Korea. The missile testing, Kim’s recent statements, the strengthening of ties between Pyongyang and Moscow and the potential of a Trump return have revived these voices. But the Yoon administration knows that any movement toward an independent nuclear deterrent would put its relations with Washington at risk and could even result in US sanctions.

Alternatively, US nuclear weapons could be redeployed on South Korean territory. They were withdrawn by the George H W Bush administration in 1991 at the end of the Cold War. Yoon raised this as a possibility during his presidential campaign last year, but the Biden administration does not support such a move which would seriously antagonise China and go against Biden’s political instincts.

The fundamental problem with the approach of the current South Korean government is that it has no chance of successfully reducing tensions. Over the past three decades, all efforts to persuade North Korea to forego nuclear weapons have failed – so engagement that is conditional on complete denuclearization is a non-starter. However, it is conceivable that the South and the North could strike some kind of deal to limit the North’s development of nuclear weapons and scale back its testing and military provocation in return for political engagement and the lifting of some sanctions. South Korea and the US could consider putting this to the test and limit the potential for serious escalation.

China and regional security

One of the key factors in the changing strategic landscape is China’s greater assertiveness. The Biden administration believes that it is confronting a more belligerent China, which now seems to have decided to expand its long-range strategic nuclear arsenal.

This, the threat to Taiwan and the South China Sea issue mean that the risk of armed conflict in East Asia is increasing, while the willingness or even ability of the US government to engage in such conflicts is coming more into question. The United States is confronting the reality that the Chinese military is in the process of modernising all of its elements, including force projection capabilities based on a large navy and air force. This means that the United States will have to both enhance its own forces in the region as well as rely more on its allies, including Australia and the United Kingdom. But this poses a potential new challenge for regional allies, namely Japan and South Korea. Although this is not yet being discussed publicly, it involves the potential participation of Japan and South Korea in conventional force projections beyond their own national self-defence.

South Korea’s nuclear dilemma

Relying on US extended deterrence creates two distinct and opposite problems for South Korea. The first is that the US nuclear guarantee may not be considered reliable by the adversary and therefore may prove ineffective. The second is that South Korea has no control over the threat or use of nuclear weapons and, therefore, could become embroiled in a conflict initiated by the guarantor. South Korea faces both of these problems although only the first is usually discussed. In order to render the nuclear guarantee more effective, forward deployment of nuclear weapons either in the region or on South Korean territory could go towards solving the credibility issue. If they are on South Korean territory, the binding effect would be quite strong because if there was a North Korean attack, the US would not allow these weapons to be lost. On the other hand, this raises other geopolitical issues regarding China. China would, without a doubt, see such weapons as a threat and indeed the United States might see a dual purpose in deterrence with regard to North Korea and China over Taiwan. The Chinese reaction could be quite severe.

Nuclear consultation arrangements that were agreed upon at the summit in April 2023 (the Washington Declaration) which included the establishment of a Nuclear Consultative Group could be a useful mechanism of reassurance for South Korea, especially if South Korea became a party to nuclear contingency plans for a Korean conflict. However, the South Korean government may fear that they might not be sufficient to enhance the deterrent with respect to North Korea, while the US may not be willing to share such secrets or commit to specific contingencies. This comes at the time when North Korea has formally abandoned the goal of Korean unification, withdrawn from all forms of engagement and interaction with the South and declared that it is preparing for war. This does not mean that armed conflict, beyond small-scale skirmishes, is likely. But linked to the global realignment, the security environment in Northeast Asia is deteriorating which creates profound challenges for the United States and its allies in the region.

The opinions expressed are those of the contributor, not of the RSAA.