Nervous Allies and Trump: NATO’s Nuclear Lesson

Key Chapter Titles

1. Balancing Strategies for Nuclear Sharing
2. Nuclear Sharing Options: Lessons Learned
3. True Sharing: Maximizing Positive Control
4. Pseudo-Sharing: The Multilateral Nuclear Force (MLF)
5. The Solution: Operational Sharing, Strategic Dependence
6. The Dubious Future of Nuclear Sharing
7. The Case of South Korea
8. Beyond Korea: Other Regional Considerations
9. Is Nuclear Sharing Worth It?
10. Conclusion: The Limits of Symbolic Compromise

Document Introduction

This study, authored by Richard K. Betts, was published in the 2025 issue of *The Washington Quarterly*. The report's core issue is that with former U.S. President Donald Trump's return to power, his questioning of and transactional attitude towards America's traditional alliance commitments have exacerbated the long-standing strategic dilemma faced by allies (particularly non-nuclear allies): on one hand, the fear of being "abandoned" under the U.S. nuclear umbrella, meaning the U.S. might be unwilling to fulfill its nuclear escalation commitments during a crisis; on the other hand, the fear of being "entrapped," meaning being dragged by the U.S. into a nuclear conflict it initiates that does not align with their own interests. This dilemma, prominent within the NATO framework during the early Cold War, has been reignited by the combined effects of current geopolitical tensions (such as the Russia-Ukraine war and North Korean nuclear threats) and declining U.S. reliability.

By systematically reviewing the evolution of nuclear weapons control arrangements within NATO since the 1950s, the report provides a historical framework for assessing current allies' potential options. The analysis covers the "true sharing" of the Eisenhower era, which emphasized "positive control" (ensuring weapons could be used promptly) while substantially relaxing regulations; the tightening of control during the Kennedy era through technical means like "Permissive Action Links (PALs)"; and the concept of the "Multilateral Nuclear Force (MLF)," which was discussed as a political compromise but ultimately abandoned. The report points out that the model NATO ultimately established and maintains to this day is "operational sharing, strategic dependence": the U.S. retains physical custody of nuclear weapons in peacetime and maintains a veto over their use through technical means, while allies only participate in operational planning. This arrangement is largely symbolic and does not grant allies the substantive capability to independently use nuclear weapons in a crisis.

Based on NATO's historical experience, the report delves into the case of South Korea, currently the most likely candidate to face the choice of nuclear sharing. Faced with North Korea's growing nuclear and missile threats and the potentially weakened security commitments of a Trump administration, significant divisions exist within South Korea (especially between the public and elites) regarding the pursuit of nuclear armament. Citing polling data, the report notes that while a majority of the South Korean public supports nuclear armament, the elite tend to be more cautious; among various nuclear options, "shared control" holds some compromise appeal for South Korean elites compared to fully independent nuclear development or maintaining the status quo. However, the report also emphasizes that the concept of "sharing" itself is ambiguous, and its strategic value depends on the actual distribution of control (the trade-off between positive and negative control). Within the framework of the U.S.-South Korea bilateral alliance, its final form may still fail to fundamentally resolve fears of "abandonment."

Finally, the report explores the applicability of nuclear sharing schemes in other regions (such as Japan and Europe) and assesses their overall value. The conclusion argues that, apart from the now-defunct Eisenhower-style "true sharing," the nuclear sharing arrangements that have appeared historically are essentially symbolic compromises between complete dependence and independent nuclear armament. As long as the nuclear-weapon-providing state (e.g., the U.S.) retains the ultimate veto over weapon use (negative control), sharing cannot substantively resolve allies' fears of "abandonment" nor prevent them from being "entrapped." In the current context of Trump's impact on the alliance system and increased strategic uncertainty, the value of such symbolic arrangements is limited and may be insufficient to assuage allies' deep-seated strategic anxieties. Ultimately, allies will still face the fundamental choice of whether to take the step towards independent nuclear armament.