For the first time, a US military unit specialized in responding to nuclear and weapons of mass destruction (WMD) scenarios conducted a training exercise in South Korea, underscoring the deepening cooperation between Washington and Seoul in the face of growing regional nuclear threats. The exercise took place on April 15 and 16, 2025, at the South Korean Strategic Command and was announced by United States Forces Korea (USFK) on April 16.
The session also included in-depth discussions on South Korea’s role in what is referred to as “Conventional-Nuclear Integration” (CNI)—a developing concept aimed at integrating US nuclear capabilities with South Korea’s conventional military forces. (Picture source: US DoD)
This inaugural session was led by two instructors from the US Army Nuclear and Countering WMD Agency (USANCA), the US military’s primary body for expertise and training in nuclear environments. The session brought together a small, specialized group of South Korean and American personnel, including six representatives from the Republic of Korea’s Strategic Command, two officials from the Ministry of National Defense, and five members of the US–South Korea Combined Forces Command. The primary objective was to build operational skills and knowledge required for operating in environments where nuclear weapons have been used or are at risk of being used.
While specific details of the training remain undisclosed, the focus was on preparing for military operations under nuclear threat conditions. The session also included in-depth discussions on South Korea’s role in what is referred to as “Conventional-Nuclear Integration” (CNI)—a developing concept aimed at integrating US nuclear capabilities with South Korea’s conventional military forces. The intent behind CNI is to establish a joint deterrence framework that is more credible, flexible, and responsive to the ballistic and nuclear threat posed by North Korea.
According to USFK, the material covered during the training is directly applicable to ongoing tabletop exercises and wargames related to CNI development. In August of the previous year, the two countries held the first such CNI-focused drill, codenamed “Iron Mace 24,” at Camp Humphreys. That exercise aimed to test joint planning procedures for deploying US nuclear assets supported by South Korean conventional forces, as part of a calibrated response to potential nuclear or missile crises on the Korean Peninsula.
Looking ahead, major bilateral exercises such as “Freedom Shield” in the spring and “Ulchi Freedom Shield” in the fall are expected to incorporate nuclear response scenarios into broader operational plans. These adjustments are intended to institutionalize extended deterrence mechanisms and ensure robust readiness between the two allies in the event of a high-intensity conflict involving WMD.
In an interview with Yonhap News Agency, Major General William Taylor, Chief of Operations at the US–South Korea Combined Forces Command, stated that although he could not discuss specific scenarios, the alliance continues refining its response strategies to prepare for all possible contingencies. His remarks reflect an ongoing effort to strengthen joint military resilience amid a security environment characterized by persistent instability and evolving asymmetric threats.
This latest exercise marks a notable step in advancing integrated nuclear defense coordination between the US and South Korea. While the CNI concept remains under development and without a finalized operational framework, these joint training activities reflect a measurable reinforcement of allied deterrence posture in the region. It also sends a direct message to Pyongyang, which continues its ballistic missile testing and efforts to enhance its strategic capabilities.
The decision to hold a joint training session focused on nuclear and WMD response reflects a broader geopolitical context, driven by several key factors.
The primary strategic rationale remains the ongoing nuclear threat from North Korea. Over recent years, Pyongyang has accelerated its ballistic missile tests, including intercontinental ballistic missiles (ICBMs) potentially capable of delivering nuclear warheads to the United States. In 2022, North Korea revised its military doctrine to allow for pre-emptive nuclear strikes, thereby increasing the credibility of potential nuclear use. In response, Washington and Seoul have stepped up military cooperation and joint exercises to deter escalation.
Secondly, the exercise aligns with US efforts to strengthen extended deterrence in the Indo-Pacific. With rising tensions not only involving North Korea but also stemming from China’s growing regional assertiveness, the United States aims to reassure its allies of its defense commitments. The inclusion of agencies such as USANCA in bilateral exercises signals a clear intent to defend allied interests through all available means, including nuclear capabilities as a last resort.
Third, the CNI concept is being developed to operationalize coordination between US nuclear forces and South Korea’s conventional military capabilities. In scenarios involving the potential use of WMDs by North Korea, the allies must be prepared to respond in a synchronized and credible manner. CNI facilitates this by enabling response planning across various levels of escalation, blending conventional and nuclear deterrence.
Finally, this initiative also reflects a political shift in Seoul’s strategic posture. Since the election of President Yoon Suk-yeol, South Korea has adopted a more assertive defense policy, including public discussions of a possible independent nuclear deterrent. Washington, in turn, has sought to reinforce bilateral cooperation to address such ambitions and maintain alliance cohesion under the US nuclear umbrella.
This WMD response training between the United States and South Korea illustrates a multi-dimensional approach to regional security challenges. It highlights the allies’ shared intent to strengthen deterrence posture, enhance joint preparedness for non-conventional threats, and develop an integrated doctrine that could shape future defense planning on the Korean Peninsula.