Towards South Korean Nuclear Weapons? Political and Strategic Considerations

Key Chapter Title List

1. Current State of the Debate in Seoul
2. Power Dynamics on the Peninsula
3. U.S. Extended Deterrence and the Second Trump Administration
4. Obstacles to Developing an Indigenous Nuclear Program
5. Conclusion

Document Introduction

This report, published by the French Foundation for Strategic Research (FRS) in January 2025, aims to delve into the possibility of South Korea seeking to develop an independent nuclear weapons capability and the associated political and strategic complexities. Triggered by South Korean President Yoon Suk-yeol's remarks in January 2023 about considering the acquisition of nuclear weapons, the report points out that as North Korea's nuclear and missile capabilities continue to advance, coupled with the uncertainty brought by former U.S. President Donald Trump's re-election in November 2024, the domestic debate in South Korea over whether it should possess its own nuclear deterrent is entering a new phase.

The report first analyzes the current state of the domestic debate in South Korea. The study indicates that although public opinion has long shown 60-70% of respondents supporting South Korea's development of nuclear weapons, with this support being particularly strong among conservative People Power Party (PPP) voters, the current discussion is more of a cacophony, filled with politically motivated statements rather than in-depth analysis of the strategic pros and cons of the options. Notably, public support for nuclear armament is not primarily driven by distrust in U.S. extended deterrence, but rather stems more from a strategic calculation that only South Korea's own possession of nuclear weapons can restore strategic balance on the peninsula and deter North Korea.

Secondly, the report assesses North Korea's military capabilities, particularly the fundamental shift in the peninsula's power balance caused by the rapid development of its nuclear and missile capabilities. By developing multiple types of intercontinental ballistic missiles (ICBMs), including those using solid propellants, North Korea has significantly enhanced the credibility and survivability of its second-strike capability. Simultaneously, its vast arsenal of short-range missiles increases the vulnerability of South Korea's critical infrastructure. In response, South Korea has developed and integrated a three-axis deterrence strategy comprising preemptive strike, massive punishment and retaliation, and missile defense, yet it still believes that conventional deterrence alone is insufficient to counter a nuclear-armed adversary.

The third section focuses on the credibility of U.S. extended deterrence, particularly the potential impact of a second Trump term. While the Biden administration attempted to strengthen security commitments to South Korea through measures like the Washington Declaration in April 2023, Trump's return introduces new uncertainties. The report notes that Trump's past transactional approach demanding allies bear more defense costs, his preference for direct engagement with North Korea, and the threat of potentially reducing U.S. troops in South Korea have all eroded Seoul's confidence in U.S. commitments. However, the report also mentions that some Republican advisors might push for a stronger deterrence posture in the Indo-Pacific, and even Trump himself, motivated by considerations like reducing U.S. costs, might harbor a degree of potential tolerance for South Korea's nuclear program.

Finally, the report details the numerous obstacles South Korea would face in developing its own nuclear program. Withdrawing from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and developing a military nuclear program would most likely lead to the rupture of the alliance with the United States and trigger automatic sanctions under relevant U.S. domestic laws, such as the Nuclear Non-Proliferation Act of 1978. Even with tacit U.S. acquiescence, South Korea would face widespread international sanctions, dealing a severe blow to its deeply integrated global economy and encountering significant technical difficulties in areas like nuclear fuel supply. Although the public seems to underestimate the consequences of sanctions, the South Korean elite are likely well aware of the enormous costs that nuclear armament would entail.

The report's conclusion emphasizes that against the backdrop of North Korea's continued nuclear arsenal modernization and increased U.S. policy uncertainty, domestic calls in South Korea for developing nuclear capabilities may intensify. However, any such policy shift would require a comprehensive weighing of its strategic implications, consequences for inter-Korean relations, changes in relations with other regional countries, impacts on the alliance system, and severe economic and technological costs. South Korea's withdrawal from the NPT would also inflict lasting damage on the already strained global nuclear non-proliferation norms. Based on a comprehensive review of public policy statements, academic research, opinion polls, and expert analysis, this report provides a professional and balanced assessment framework for understanding this highly complex strategic issue.