In the Washington Declaration signed in May 2023, the United States and South Korea agreed to enlarge the scope of their security cooperation. Among various issues, cooperation related to nuclear deterrence against North Korea was included. Washington showed its willingness to consult with Seoul over the possible deployment of nuclear weapons in South Korea to deter North Korean aggression.

Moreover, both countries discussed nuclear strategic planning and contingency through a newly established Nuclear Consultative Group (NCG).[1]

Although the United States solidified its security guarantees for South Korea during the Biden Administration, the side effects caused by the alliance and the changing regional strategic environment generated a sense of insecurity for South Korea. Prior to Biden’s presidency, the Trump administration attempted to reduce Washington’s security commitment to South Korea.[2] Meanwhile, Washington’s “Indo-Pacific” Strategy tries to mobilize Seoul to counterbalance China collectively.[3]

In this respect, Washington’s approach has triggered Seoul’s abandonment and entrapment anxieties.

In response to the current strategic environment in Northeast Asia, President Yoon Suk Yeol suggested South Korea should develop indigenous nuclear weapons in 2023.[4] Yoon’s statement triggered debate about South Korea’s nuclearization amongst the South Korean public. Current policy debate and review on this issue focus on the reasons South Korea should develop its own nuclear weapon and the public attitude toward this issue. However, given the contentious nature of this issue, deeper discussion is necessary.

Current research and policy review focus on the factors behind and the possible consequences of South Korea’s nuclearization. Facing North Korea’s frequent provocations and the side effects of the U.S.-ROK alliance (both the abandonment and entrapment anxieties), developing nuclear weapons would help South Korea defend itself from external threats and enhance South Korea’s autonomy vis-à- vis the United States.[5] However, opponents argue that South Korea’s nuclear weapons development may undermine South Korea’s international reputation, trigger Washington’s abandonment of Seoul, and exacerbate the security dilemma in the region.[6] Beside security factors and the possible results of nuclear weapons development, details related to this agenda deserve deeper investigation.

First, it is necessary to explore the gap between the public and the elites’ concerns about the agenda of South Korea’s nuclear weapons development. Political elites are more concerned about its negative consequences. As a signatory of the Nuclear Non-proliferation Treaty (NPT), Seoul’s nuclearization would violate the commitments it made to the international community. In the long run, not only are the elites concerned about possible sanctions against South Korea, but they also feel anxious about whether nuclear weapons development would undermine South Korea’s image internationally.[7] Moreover, the elites are concerned about the possible deterioration of the security dilemma in Northeast Asia. North Korea would be more aggressive if South Korea develops nuclear weapons. In the most extreme case, North Korea may launch a pre-emptive attack to constrain Seoul’s nuclear weapons development.[8]

Compared with the elites, the public is more concerned about the effectiveness of nuclearization in ensuring the country’s sovereignty and security. For instance, the public believes that nuclear weapons development would enhance South Korea’s capabilities in relation to risks in the region and enhance Seoul’s bargaining power vis-à-vis neighboring countries.[9] Specifically, in addition to counterbalancing North Korea’s provocations and nuclear threat, the public believes that developing nuclear weaponry would help enhance South Korea’s autonomy in the U.S.-ROK alliance. Not only would nuclear weapons reduce abandonment anxieties when Washington is reluctant to provide support to Seoul, but also would help South Korea ensure its position amidst the power competition between Washington and Beijing.[10] In this regard, the elites in South Korea are more concerned about the impact of South Korea’s nuclearization for the country’s international reputation and the regional security environment, whereas the public is more concerned about the positive impacts of nuclearization in ensuring South Korea’s security and sovereignty.

In addition to the gap between the elites and public over their attitude toward South Korea’s nuclearization, it is important to explore the methods through which South Korea could obtain or develop nuclear weapons Based on the current circumstance, South Korea can either obtain nuclear weapons from the U.S. or develop indigenous nuclear weapons. Admittedly, there are some suggestions that the NATO model could be applied to South Korea’s pursuit of nuclear weapons. Similar to NATO countries, South Korea can promote security cooperation with neighboring countries to obtain nuclear weapons.[11] However, it is unlikely that South Korea would adopt the NATO model due to Washington’s opposition and the inability of regional countries to promote nuclear cooperation with South Korea.[12] If it is not possible to adopt the NATO model, South Korea could only receive nuclear weapons from the United States, including the re-deployment of tactical nuclear weapon or the introduction of related weapons into South Korean territory

Alternatively, if South Korea considers developing indigenous nuclear weapons, it is essential to consider “how” to develop those weapons. Specifically, technical issues such as obtaining the required resources and facilities for developing a nuclear arsenal deserve deeper consideration. Moreover, it is necessary to consider which types of nuclear weapons should the country pursue, such as traditional types of nuclear weapons or tactical nuclear weapons.

Furthermore, it is important to consider the negative effects that would be generated during the process of nuclear development. Admittedly, international relations-related (IR-related) literature concludes that there are some incentives for states to develop their own nuclear capabilities. For instance, nuclear weapons as an instrument to ensure the country’s sovereignty, security, as well as enhance national dignity.[13] Imagine if South Korea were to become a nuclear power, it would have greater capability to deter North Korea’s aggression. South Korea would also enhance its sovereignty vis-à-vis the alliance with the United States and enhance its bargaining power over regional security issues.[14] However, negative consequences resulting from the process of nuclear development deserve closer attention. In addition to possible strong economic sanctions against South Korea, diplomatic and security side-effects as a consequence of the process of nuclear development need to be considered during the discussion of this agenda. As mentioned before, South Korea’s nuclear development would likely exacerbate North Korea’s aggression against South Korea. The United States may also withhold its commitment to South Korea, thereby increasing the level of abandonment anxiety of Seoul.

Finally, domestic circumstances in the United States and South Korea play an essential role in the agenda. The United States expanded the scope of security cooperation with South Korea during the Biden administration. For instance, Washington established the NCG to strengthen policy communication with South Korea related to the use of extended deterrent against North Korea and deployed a ballistic missile submarine and strategic bombers to South Korea.[15] However, after President Trump came into office in 2025, he has reduced the support for U.S. allies, the same as in his first term 2016- 2020. There is no guarantee that the United States will maintain the same level of security cooperation with South Korea after President Trump came into office in 2025.[16]

In addition, domestic circumstances have played an essential role in South Korea’s foreign policy making since 2024. Due to the declaration of martial law in December 2024, the Constitutional Court agreed to impeach President Yoon Suk Yeol in April 2025, leading to a leadership transition in June 2025.[17] Under such a circumstances, there is an uncertainty about whether the incoming president of South Korea will support nuclearization and which foreign policy preferences would be chosen in the face of the challenges in the region.

Overall, without considering the aforementioned issues, there is difficulty in examining the costs of South Korea developing nuclear weapon. Thus, we cannot conclusively evaluate whether the benefits of developing nuclear weapons could outweigh the costs and whether nuclear weapons would actually help ensure South Korea’s security and sovereignty.

Facing the changing strategic environment in Northeast Asia, more voices in South Korea suggest that the country should develop nuclear weapons to ensure its security and sovereignty. The existing discussion on this agenda focuses on whether South Korea should nuclearize itself, and the underlying reasons behind this agenda have become a topic of debate. However, details related to this agenda deserve deeper discussion and observation. Based on observations of the current debate on South Korea’s possible nuclear weapons development, some policy implications are as follows.

First, more policy communication regarding South Korea’s nuclear development between the policy elites and the public is essential. The South Korean public has become more in favor of nuclear weapons development since it would help ensure South Korea’s security and autonomy when facing the security dilemma in the “Indo-Pacific” region; the elites are more concerned about the negative consequences of nuclear weapons development for the country’s reputation and the security environment in Northeast Asia. The gap between both sides could be narrowed if there was more policy communication regarding this issue.

Second, deeper discussion of the technical issues and the possible outcomes of the nuclear development process is essential. Developing nuclear weapons is a time-consuming process and requires huge investment. In addition, the process of nuclear weapons development would place South Korea in a vulnerable position. In this regard, discussion of technical issues and the possible impact during the development process is an opportunity for policymakers and the public to examine whether this policy option is suitable for South Korea to ensure its national security. Even if the country pursues nuclear weapons, consideration of those issues would help Seoul reduce those side effects during the process of nuclear weapons development.

Besides discussion in the country, communication between Washington and Seoul on nuclear and regional security would help solidify the alliance. In fact, overcoming the abandonment and entrapment anxieties related to the alliance is an important factor influencing South Korea’s preference for pursuing nuclear weapons.

There is apprehension about Washington’s adoption of a distancing policy if Seoul intends to develop nuclear weapons. Policy communication between both sides would help enhance South Korea’s confidence in the alliance. In the most ideal case, this will help both sides to come up with policy options that fulfill the interests of both countries.