Nuclear Weapons Cooperation in US Alliances

11 October 2022

Nuclear weapons remain central to the internal dynamics of US alliances in Europe and the Indo-Pacific. But cooperation related to them has varied significantly between allies and over time.

In NATO, the US continues to ‘share’ nuclear warheads with several of its allies for delivery by their air forces, and the alliance jointly develops nuclear policy and declaratory statements on nuclear deterrence. But while Germany made significant use of these opportunities for cooperation during the Cold War and beyond, Norway – also a frontline ally – actively limited the role of nuclear weapons in its cooperation through NATO. In contrast, in the Indo-Pacific, South Korea had essentially no insight or say in the stationing of US nuclear weapons on its territory, while Japan negotiated a set of secret understandings regarding nuclear weapons and US bases in Japan. In both countries, US nuclear weapons have been withdrawn since 1991, but unlike Australia, which never had US nuclear weapons on its territory, both Japan and South Korea both established fora for formal policy consultation and discussion on deterrence and nuclear weapons with the United States.

With the assistance of grants from the Australian Research Council (ARC) and Department of Defence, Professors Stephan Frühling (ANU) and Andrew O’Neil (Griffith University) examined the history of US nuclear weapons cooperation in the Cold War and beyond, across alliances in Europe and Asia. They used this to test realist and institutionalist approaches to explaining alliance cooperation, and examined implications for the future of US alliances and Australian defence policy.

Based on in-depth case studies of cooperation on US nuclear weapons in Germany, Norway, Japan, South Korea and Australia, the project shows that contrary to realist theory, US allies have wielded significant influence in shaping nuclear weapons cooperation with the US in ways that reflect their own, often idiosyncratic, objectives. US allies have at times reduced, and in some cases declined, material cooperation that would have visibly linked US nuclear weapons to their own security. In general, this reflected their own assessments of the role of US nuclear weapons in allied security, which demonstrates that the value of nuclear weapons for security is not fixed, and ‘nuclear strategy’ is a negotiated and contested concept between allies. Alliances are more than mere tools of external balancing, and structured cooperation on US nuclear weapons has been a deliberate tool to promote policy convergence within them.

Nuclear weapons cooperation has been a crucial factor in reinforcing institutional commitment within alliances and achieving consensus on strategic priorities. It promotes alliance cohesion at times when that cohesion is potentially threatened by perceptions of differing strategic priorities among allies. Rather than being a bargain in its own right, nuclear weapons cooperation creates the basis of trust and commitment upon which allies are then able to negotiate–and strike–the necessary deals on burden-sharing and alliance strategy.

This has significant implications for the role of nuclear weapons and deterrence in US alliances today. US allies therefore need to become more embedded in, and proficient with, discussions with Washington over escalation and nuclear deterrence. To achieve closer integration and strengthen multilateral deterrence, the United States and its Indo-Pacific allies need to develop a shared understanding of escalation dynamics; maintain political unity about a shared approach to deterrence; move from consultation to joint assessment, policy and planning; conduct reviews of alliance force structure and posture and their implications for escalation; and engage in public campaigning for nuclear deterrence.

All of these are all mutually reinforcing. In combination, they would be transformative for US alliances in the Indo-Pacific, because they involve accepting a degree of heightened strategic risk that many allies have so far eschewed. Failure to agree on expectations and commitments in relation to deterrence and escalation pathways runs the risk of the US and its allies not being able to take unified action during a crisis.

Longer term, these findings also raise the question of what a greater role for nuclear weapons in US alliances in the Indo-Pacific might look like. Calls for ‘nuclear sharing’ of US warheads are rising in South Korea and Japan. Historically, forward-based nuclear weapons have helped in ‘coupling’ to US strategic forces, in the creation of inadvertent risks of escalation for potential adversaries, and in facilitating limited nuclear use options. While all of these would also be relevant for a return of US nuclear weapons to the territory of Indo-Pacific allies, the project suggests that the increased political and military integration in these alliances that could be catalysed by nuclear weapons cooperation could be even more consequential.

Book launches
Based on this research project, Professor Frühling and Professor O’Neil have published two books: Partners in deterrence: US nuclear weapons and alliances in Europe and Asia and Alliances, Nuclear Weapons and Escalation: Managing Deterrence in the 21st Century. Reviews of these books have been published in the Australian Journal of Defence and Strategic Studies, Comparative Strategy, and International Affairs.
The Coral Bell School of Asia Pacific Affairs held book launches for the aforementioned titles. The book launch for Partners in deterrence saw lively discussion, and the book launch for Alliances, Nuclear Weapons and Escalation was launched by Japanese Ambassador His Excellency Yamagami Shingo. Video recording of both book launches can be found on the event pages.

Policy report and interviews
A policy report analysing current policy challenges of Australia’s engagement with US nuclear deterrence has been published at the University of Sydney’s United States Studies Centre website.
Professor Frühling was interviewed by David Trachtenberg, where he discussed the rise of China and what it means for security relationships in the Indo-Pacific region, drawing inference from his research on alliances.

Published articles and blogs
Apart from two books, Professors Frühling and O’Neil have co-published four academic articles that explored the project findings and their implications for current challenges in US alliances:
- Alliances and Nuclear Risk: Strengthening US Extended Deterrence
- Institutions, informality, and influence: explaining nuclear cooperation in the Australia-US alliance
- Nuclear weapons and alliance institutions in the era of President Trump
- Nuclear weapons, the United States and alliances in Europe and Asia: Toward an institutional perspective

Moreover, they have written several commentary pieces over the years that draw from their extensive research. Two blog posts titled, ‘Nuclear deterrence and the US–Australia alliance’ and ‘Making Indo-Pacific alliances fit for deterrence’ have been written for Australian Strategic Policy Institute’s online publication The Strategist. Two posts titled ‘Nuclear Ban Treaty: Wishful thinking over realism’ and ‘A “No-First-Use” doctrine would undermine American nuclear deterrence’ were written for Lowy Institute’s The Interpreter. ‘Implications of the US Exit From the INF Treaty’ was co-authored for the Australian Institute of International Affairs’ Australian Outlook and ‘Donald Trump and Nuclear Cooperation: the Art of the Deal’ was written for the Contemporary Security Policy blog.

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