In a significant step toward bolstering allied preparedness against nuclear threats in Northeast Asia, the U.S. Army’s premier nuclear and weapons of mass destruction (WMD) response unit has conducted its first-ever nuclear effects training on South Korean soil. The joint effort marks a new level of coordination between U.S. Forces Korea (USFK) and the Republic of Korea (ROK) military as the two allies continue to refine their joint deterrence strategies in the face of North Korea’s expanding nuclear arsenal.
The training, held April 15–16 at South Korea’s Strategic Command headquarters, was led by instructors from the U.S. Army Nuclear and Countering WMD Agency (USANCA), a specialized arm of the Army responsible for nuclear survivability, response, and operational support. The event brought together key personnel from both countries, including six representatives from South Korea’s Strategic Command, two officials from the Ministry of National Defense, and five members from the U.S.-ROK Combined Forces Command.
According to a USFK statement, the two-day session focused on operations in environments where nuclear weapons may be used or their use threatened. Although specific scenarios and tactics remain classified, officials said the training covered the foundational knowledge and operational planning necessary for functioning in high-risk nuclear contingencies.
“This type of training ensures that we are not only aware of the effects of nuclear weapons but are also able to operate effectively under such conditions,” USFK noted in a statement released April 17. “It is a vital step in strengthening combined readiness.”
While the United States and South Korea have long conducted joint military drills, this latest training underscores a strategic shift toward deeper integration of nuclear and conventional forces through a concept known as Combined Nuclear and Conventional Integration (CNI). Still in development, CNI aims to create a seamless operational framework that merges U.S. nuclear capabilities with South Korea’s cutting-edge conventional weaponry.
Though a formal CNI doctrine has not yet been finalized, military leaders view the concept as central to future deterrence efforts in the region. “This training can be directly applied to alliance CNI tabletop exercises and war games,” USFK stated, suggesting that these nuclear-focused sessions will increasingly form the backbone of future operational plans.
In August 2024, the two countries held their first CNI tabletop exercise (TTX), codenamed Iron Mace 24, at Camp Humphreys, the largest U.S. military installation in South Korea. That exercise emphasized joint planning procedures for scenarios involving the potential deployment of U.S. nuclear weapons with South Korean conventional support. Officials said it also tested alliance command-and-control systems and cross-domain coordination to counter North Korea’s growing missile and nuclear threats.
The renewed focus on nuclear operations is largely driven by rapid developments in North Korea’s military capabilities. Over the past two years, Pyongyang has tested multiple long-range ballistic missiles capable of striking the U.S. mainland and has unveiled what it claims to be tactical nuclear warheads designed for battlefield use.
North Korea’s provocative actions have reignited security concerns in Seoul and Washington, pushing the allies to prepare for a broader range of contingencies, including the possibility of limited nuclear use in a conflict scenario.
“While I can’t discuss specific scenarios, the alliance continues to refine its response strategies to be prepared for any contingency,” said Maj. Gen. William Taylor, operations chief at the U.S.-South Korea Combined Forces Command, in an interview with Yonhap News Agency earlier this month. “Deterrence is not static; it must evolve with the threat landscape.”
That evolution is evident in recent developments. During the Freedom Shield exercise in March, and the Ulchi Freedom Shield drill scheduled for August, nuclear-related scenarios are being increasingly incorporated into the operational planning. These exercises, which simulate large-scale conflict situations, now routinely include nuclear contingency modules designed to evaluate command responsiveness, civil defense measures, and combined retaliation protocols.
The timing of the nuclear effects training is unlikely to be lost on Pyongyang—or Beijing. Both the United States and South Korea have emphasized that the recent activities are defensive in nature, but analysts note that such highly specialized training also sends a clear message to adversaries.
“Joint nuclear effects training in South Korea is not just about readiness—it’s also about signaling resolve,” said Dr. Min Ji-Hoon, a defense analyst at Seoul’s Institute for Strategic and International Studies. “It tells North Korea that the alliance is preparing for all scenarios, including those involving nuclear weapons. And it tells China that the U.S. nuclear umbrella in Asia remains intact and evolving.”
Indeed, Washington has reaffirmed its extended deterrence commitment to South Korea multiple times over the past year. High-level dialogues between U.S. and South Korean defense officials have increasingly focused on the credibility of the nuclear umbrella, with some South Korean lawmakers even advocating for the redeployment of tactical U.S. nuclear weapons to the peninsula—a notion the Biden and Trump administrations have not publicly endorsed.
Instead, efforts have centered on joint planning, improved strategic communication, and the development of integrated response protocols. The latest training session reflects that approach: preparing forces to operate in a nuclear-threat environment without escalating to nuclear use themselves.
Beyond the strategic implications, the training also serves a more practical purpose: building institutional knowledge across ranks and agencies. For many of the South Korean participants, this was their first exposure to formal U.S. nuclear doctrine and survivability strategies.
“Training like this enhances interoperability, not just in systems, but in understanding,” said a U.S. defense official familiar with the event. “If a crisis were to occur, we need to be speaking the same language—literally and doctrinally—when it comes to nuclear effects and operations.”
USANCA, the lead U.S. agency in the training, specializes in exactly that. Its mission is to advise Army and joint force commanders on nuclear survivability and operational resilience in WMD environments. Their presence in South Korea signals a maturing alliance relationship—one where sensitive, high-level knowledge is being actively shared and applied.
While the April training marked a milestone, officials suggest it is just the beginning. Future iterations are expected to broaden in scope and include participants from additional U.S. service branches and South Korean government agencies.
Plans are also underway to integrate nuclear effects considerations into other combined exercises and potentially expand the CNI concept into a standing doctrine. For that to happen, however, both nations must overcome political and logistical hurdles, including the delicate balance of public opinion in South Korea regarding nuclear policy.
Nonetheless, military leaders on both sides appear committed to moving forward.
“The alliance is stronger when we prepare together,” Maj. Gen. Taylor said. “This training is about more than tactics. It’s about trust, communication, and a shared understanding of what it takes to deter and, if necessary, defend.”
As North Korea continues to advance its nuclear ambitions, that shared understanding may prove to be the most critical weapon of all.
