Nuclear Puzzles: What can South Korea Learn from NATO’s Experiences as a Nuclear Alliance?

CSDS POLICY BRIEF • 36/2024

By Jina Kim and Luis Simón

28.11.2024

Key issues

• The advances in the Democratic People’s Republic of Korea’s (DPRK) nuclear and missile programmes have reinvigorated discussions about the merits, drawbacks and possible modalities of a Republic of Korea (ROK) nuclear capability.
• Although Washington’s interest in reassuring Seoul and preventing proliferation have been a key driver of the United States (US)-ROK alliance in recent years, the election of Donald Trump now adds a new dimension to the ROK’s nuclear debates.
• NATO’s experience as a nuclear alliance holds a number of lessons for the ROK both in relation to the pros and cons associated with various nuclear pathways, as well as the need to see nuclear and conventional forces as interwoven in the context of nuclear strategy.

Introduction

This CSDS Policy Brief examines to what extent NATO’s experience as a nuclear alliance can yield relevant lessons for the Republic of Korea (ROK). The brief zooms in on two sets of potential lessons. First, we consider the various alternative nuclear pathways available to the ROK (i.e. as illustrated by ongoing debates about the benefits of an indigenous capability vs. some form of nuclear-sharing arrangement with the United States). Second, we analyse doctrine including the ongoing ROK debates on whether a nuclear attack warrants a nuclear response and the relationship between nuclear and conventional capabilities in the context of extended deterrence. We begin by providing an overview of the evolving nuclear debate in South Korea to then examine the possible lessons (or lack thereof) that could be drawn from NATO’s experience.

The growing appeal of nuclear weapons in the ROK

Recent advances in the DPRK’s nuclear and missile programmes, Pyongyang’s growing nuclear assertiveness and ongoing concerns about the reliability of US extended nuclear deterrence have fueled public debate on the merits, drawbacks and possible modalities of a ROK nuclear capability. If anything, this debate has become even more pressing following the election of President Donald Trump, with some South Korean experts and policymakers having recently expressed concerns about the possibility that the US may cut a deal with the DPRK over the ROK’s head. Such concerns already surfaced during the first Trump administration, amidst speculation that Washington and Pyongyang entertained a possible deal to dismantle the DPRK’s Intercontinental Ballistic Missiles (ICBMs), which Pyongyang can target the continental US with – while excluding short and medium range missiles, which can target the ROK and spare the US.

To be sure, the Trump administration’s insistence on Complete, Verifiable and Irreversible Denuclearisation (CVID) led to the collapse of a potential comprehensive agreement, as negotiations over US sanctions relief and verification measures broke down. In light of North Korea’s advancement in asymmetric capabilities – such as the development of hypersonic missiles and diversification of missile platforms – implementing effective risk reduction strategies has become increasingly imperative.

Recent polls signal considerable support amongst the South Korean public for some form of nuclear pathway. However, support for South Korea’s acquisition of nuclear weapons has varied over time: peaking at 71.3% in 2021, decreasing to 69% in 2022 and 60.2% in 2023, before rising again to 66.0% in 2024. Conversely, trust in the US nuclear umbrella has declined from 72.1% in 2023 to 66.9% in 2024. While overall confidence in the US-South Korea alliance remains high, these trends suggest underlying concerns about the adequacy of the current nuclear deterrent posture against North Korea, as reflected in public opinion on nuclear armament.

Donald Trump’s election in 2024 has reignited concerns about South Korea’s security posture. Notably, certain lawmakers from the People Power Party (PPP) have advocated for a more assertive stance in negotiations with President-elect Trump, suggesting Seoul should consider developing its own nuclear arsenal. In contrast, the South Korean government has reaffirmed its opposition to nuclear armament, emphasising that strengthening extended deterrence is the most realistic and desirable policy option. Put in perspective, this divergence indicates that the debate over South Korea’s defence strategy is likely to remain a contentious issue.

To be sure, growing public support for a nuclear pathway in South Korea precedes the election of Donald Trump. Indeed, such support and Washington’s interest in both reassuring its South Korean ally and preventing proliferation, have been key drivers of US-ROK alliance politics in recent years. Concretely, the 2023 Washington declaration between the United States and the ROK, and the establishment of a new Nuclear Consultative Group (NCG), had the double purpose of bolstering allied deterrence against the DPRK threat and reassuring South Korea about the credibility of US extended deterrence.

The Washington Declaration and setting up of the US-ROK NCG have created a new dynamic within the US-ROK alliance. Some of the measures recently adopted include a commitment to: move towards greater integration of US and ROK early-warning systems and streamline intelligence sharing; step up US strategic asset visits to the Korean Peninsula (espeically nuclear submarine port calls and strategic bomber visits); increase US-ROK tabletop exercises around nuclear contingencies; and a commitment by the US president to make every effort to consult with South Korea’s president before using a nuclear weapon on the peninsula. Despite the establishment of an institutional framework, the Korean media has been preoccupied with comparing the NCG to Europe’s Nuclear Planning Group (NPG), raising concerns about its limitations.

The South Korean Ministry of National Defense and the Joint Chiefs of Staff have prioritised the integration of nuclear and conventional forces to effectively counter North Korea’s escalating nuclear and missile threats. In November 2022, the military expanded and reorganised the Nuclear and WMD Response Center under the Strategic Planning Headquarters to enhance deterrence and response capabilities. Building on this initiative, in June 2024 South Korea proposed legislation to establish a “Strategic Command” aimed at integrating and commanding the military’s strategic assets. This move reflects an intention to closely coordinate with US strategic operations, thereby strengthening the alliance’s combined deterrence posture.

Trilateralising extended deterrence discussions with Tokyo is supposed to offer an additional venue to reassure the ROK in the face of the growing DPRK threat. While nuclear deterrence in a US-Japan-ROK setting remains an elusive goal, greater trilateral cooperation in Ballistic Missile Defence (BMD) appears to offer some promise. In this regard, the 2023 Camp David Agreements between Washington, Seoul and Tokyo have ushered in a new era of trilateral defence cooperation around the DPRK threat, with a specific focus on BMD cooperation.

While these measures may have helped reassure South Korea, the DPRK’s ongoing bellicosity and longstanding questions about the reliability of the US guarantee continue to fuel debates about nuclear weapons in South Korea. To what extent, if at all, can NATO’s experience as a nuclear alliance yield relevant lessons for the ROK?

Lessons from NATO

Of course, any comparison between NATO’s and the ROK’s nuclear predicaments should proceed with extreme caution. The Asia-Pacific is a predominantly maritime strategic environment based on a bilateral or “hub-and-spokes” alliance ecosystem that is populated by several nuclear adversaries (i.e. China, DPRK and Russia). In contrast, Europe is a predominantly continental environment based on a multilateral alliance and primarily one nuclear adversary (e.g. Russia).

However, while the differences between Europe and Asia can hardly be overstated, they can also be just as easily overblown. For one thing, the maritime vs. continental distinction becomes much blurrier in a Korean peninsula context, which remains a predominantly air-land theatre in strategic terms. For another, multilateralism and bilateralism are ideal types and often analytically meaningless categories. NATO can arguably be depicted as a collection of bilateral alliances, in that the most significant factor for protégés – insofar as deterrence and assurance are concerned – is their bilateral relationship with the US. Moreover, the proliferation of bilateral and minilateral frameworks for defence cooperation in Europe, and growing spoke-to-spoke and minilateral defence cooperation in Asia, are leading to more “hybrid” or “nodal” structures in each region. Third, Iran’s nuclear and missile advances and China’s own military modernisation also present Europeans with a “multiple nuclear adversary” dilemma.

Therefore, and notwithstanding all the differences between Europe and Asia, NATO’s rich experience in all things nuclear can conceivably yield some valuable lessons for the ROK.

Nuclear pathways

When thinking of alternative nuclear pathways, NATO’s rich experience with different degrees of nuclear (in)dependence can yield some interesting lessons about the pros and cons of alternative nuclear pathways. For example, France offers the most independent pathway in the sense that it is technologically indigenous, relatively robust (two legs) and less obligations (no part of NATO’s NPG). On the flip side, maintaining and modernising the nuclear deterrent absorbs a huge share of French defence spending, thus limiting France’s bandwidth in the conventional space. Experts typically allude to that as a tradeoff between strategic or rhetorical independence and tactical and warfighting excellence, associating France with the former and the United Kingdom (UK) with the later.

The UK’s nuclear deterrent is arguably less independent than France’s in several ways. First, it depends on US-manufactured systems. Second, it stands only on one leg. And third, NATO and the NPG are the main referent for the UK deterrent. A lower level of nuclear autonomy means Britain trades (rhetorical) independence for operational effectiveness, as illustrated by its higher degree of nuclear collaboration with the US, full integration in NATO’s deterrence architecture and devotion of fewer resources to its deterrence, which leave more bandwidth for conventional warfighting capabilities. So, we have in Britain a different approach to deterrence whereby an operationally autonomous nuclear capability is part of a broader picture that blends nuclear and conventional forces, and where the NATO framework and special relationship with the US hold a prominent position.

Additionally, there are countries operating Dual Capable Aircraft (DCA) including Belgium, Germany, Italy and the Netherlands. Of course, the main downside of this option when compared with an indigenous capability is that DCA countries do not have the ability to decide whether a nuclear weapon is used; ultimate authority rests with the US. However, one benefit is that DCA countries do have a veto on whether DCA capabilities are used (i.e. once the US approves use) and also have a say on how they are employed. A related benefit is that DCA countries have much more insight into how nuclear deterrence operates. Additionally, the combination of high scientific, technical development and operational experience with nuclear weapons gives nuclear sharing countries proper latency.

All other NATO countries – except for France – participate in the NPG, which provides a forum for consensual decision‑making relating to deterrence communication, nuclear planning and force posture, consultation about nuclear use, nuclear weapons safety and arms control issues. Non-DCA members of the Nuclear Planning Group are probably closest to the situation the ROK finds itself in following the creation of the Nuclear Consultative Group with the United States. That said, the level of consultaton is deeper and more developed in a NATO context, because the extended nuclear deterrence architecture is more mature. However, a bilateral framework as opposed to having 31 countries around the table provides a lot more potential.

Doctrine

Nuclear sharing in a NATO context has been underpinned by a three-fold logic: 1) restrain proliferation; 2) cement allied cohesion; and 3) strengthen deterrence by providing a wider array of graduated force options. These three logics underpinned NATO’s experience with nuclear sharing throughout the Cold War and beyond. However, the fact is that there is no such thing as “extended nuclear deterrence”. In reality, there is only “extended deterrence”, where nuclear and conventional forces must be seen as interwoven in the context of overall nuclear strategy.

Whether NATO has relied more on nuclear or conventional forces, and inched closer or further from the “nuclear-for-nuclear” principle – i.e. the notion that a nuclear attack warrants a nuclear response – has depended on a dynamic strategic context. Two examples help illustrate this point. First, when, in the late 1950s, Soviet conventional military power began to significantly outmatch NATO, the Alliance faced a dilemma: to dramatically increase defence expenditures to sustain adequate conventional defences, or, alternatively, to double-down on its reliance on nuclear deterrence. The result was the promise of massive retaliation, which even included the possibility to respond with nuclear weapons to a conventional Soviet attack to avoid NATO forces from being overrun. But this would not prove sustainable. Second, once the Soviet Union developed ICBMs, the Alliance embraced a strategy of flexible response. Critically, in the 1980s, the Alliance’s investment in innovative (conventional) operational concepts and capabilities, including advanced missile defences, helped offset the Soviet Union’s numerical conventional and nuclear advantage in the theatre, and helped to ultimately throw the Soviet military off-balance.

Conclusion

For all the differences between Europe and Asia, NATO’s trajectory as a nuclear alliance may offer some valuable lessons in the context of South Korea’s intensifying debates about nuclear deterrence.

For one thing, NATO’s rich experience with different degrees of nuclear (in)dependence can yield interesting lessons about the merits and drawbacks of alternative nuclear pathways. The indigenous or independent nuclear deterrent option – pursued by France and, to a lesser extent, Britain –  surely affords a greater degree of independence and thus security, but it comes with a heavy price tag and entails high opportunity costs, especially when it comes to conventional modernisation. In turn, nuclear sharing may not allow the ROK to decide whether nuclear weapons are used, but would give it veto power over whether they are used and a say on how they are used (i.e. nuclear force employment). It also provides significant insight into how nuclear deterrence operates, thus affording proper ‘latency’ and contributing to assurance. Lastly, extended nuclear consultations offers an insight and a say over deterrence communication, nuclear planning and force posture, consultation about nuclear use, nuclear weapons safety and arms control issues, thus contributing to greater nuclear literacy. That said, it has few concrete benefits in terms of either deterrence or assurance.

Finally, when it comes to doctrine, a key takeaway from NATO’s experience throughout the Cold War and beyond is the fact that there is no such thing as extended nuclear deterrence: there is extended deterrence, and nuclear and conventional forces must be seen as interwoven in the context of nuclear strategy.

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