At the August 18 ROK-U.S.-Japan trilateral summit held at Camp David, the three leaders declared that “By the end of 2023, we intend to operationalize our sharing of missile warning data on the DPRK in real-time … We are committed to pursuing enhanced ballistic missile defense cooperation to counter DPRK nuclear and missile threats.” Given the increasing North Korean nuclear threat, security collaboration between South Korea, the United States, and Japan is not optional but rather a critical necessity. The consolidation of missile defense capabilities among the three nations is especially required to address the challenge posed by North Korean ballistic missiles with nuclear warhead capabilities.

Some have questioned whether trilateral missile defense cooperation among the three nations signifies South Korea’s incorporation into the U.S.-led missile defense (MD) system with Japan’s participation and whether it is a “ROK-U.S.-Japan trilateral alliance.” Due to the unprecedented state of the North Korean nuclear threat, South Korea needs to boldly transition to a mindset of “thinking about the unthinkable.” Considering the detection, tracking, and interception capabilities possessed by the MD systems of the United States and Japan, South Korea must proactively propose and lead the establishment of an integrated MD system to leverage these assets for our use and facilitate cooperation.

The integration of the MD system entails joint operation of the entire command and control, detection and tracking, and interception processes by South Korea, the United States, and Japan. With this arrangement, the United States can treat an attack on South Korea with nuclear weapons as equivalent to an attack on itself, allowing for an immediate and automatic nuclear response. It is the establishment of the framework under which South Korea can intercept intercontinental ballistic missiles (ICBMs) targeting the United States and, to intercept diverse short-range ballistic missiles aimed at the Korean Peninsula, the United States can use its military assets in South Korea, U.S. bases in the Indo-Pacific, and potentially those in the mainland if necessary.

The core of an integrated MD system lies in early warning and information sharing among the three countries, driving strategic decisions through close consultation among leaders in the initial stages of North Korean nuclear and missile threats. Once strategic decisions are reached through consultation and agreement among the leaders of the three nations, the processes leading to response and interception can be executed according to their respective national command and control systems. Of course, ensuring mutual coordination between command and control systems is imperative for post-decision actions such as trajectory tracking, interception, and information assessment. For that, it is crucial to secure “interoperability.”

Viewing North Korea’s nuclear and missile threats as a collective challenge for South Korea, the United States, and Japan within the integrated MD system, it is imperative that we transition from a primarily terminal-phase-oriented interception system aimed solely at defending the Korean Peninsula to a system capable of intercepting missiles heading towards the U.S. mainland. Establishing interoperability between South Korea’s indigenously developed medium-altitude and low-altitude interceptor missiles and the MD systems of the United States and Japan would be a valid approach.

Above all, South Korea must have access to the sharing of information and interception assets from the integrated MD system with the United States and Japan. In particular, the priority is real-time information sharing from the Space-Based Infrared System (SBIRS) utilizing advanced surveillance satellites. By employing SBIRS, it is possible to closely detect developments related to North Korea’s nuclear and missile launches, thereby enabling clear conclusions about imminent attack intentions and determining pre-emptive strike options.

In addition, more time is secured to intercept North Korean missiles, allowing for follow-up interceptions even if the initial interception fails. Currently, we rely solely on radar to detect North Korean missile launches, which takes about 30 seconds to one minute after the missile is launched for detection to be possible. Since it takes approximately five to eight minutes for North Korean missiles to reach significant targets within South Korea, gaining an extra 30 seconds to one minute would enhance the possibility of additional interceptions, significantly enhancing our security. With its possession of eight reconnaissance satellites and early warning assets, Japan can conduct surveillance and reconnaissance of North Korea from various angles and distances, facilitating accurate information assessment, thus underscoring the need to pursue information sharing with Japan.

The ultimate purpose of an integrated MD system is not just responding after the actual use of nuclear weapons or missiles by North Korea or other forces but also to “deter” such weapon systems from being employed. An “integrated” ROK-U.S.-Japan MD system should be linked with “integrated extended deterrence.” To deter North Korea’s nuclear and missile threats, it is crucial to create the impression that the use of nuclear weapons will lead to unavoidable nuclear retaliation. In this sense, it is necessary to explore innovative approaches to strengthening extended deterrence that go beyond the Washington Declaration such as the redeployment of tactical nuclear weapons.

Moreover, there is a need to work with Japan as another potential target of North Korea’s nuclear and missile threats on policies to bolster the U.S. extended deterrence commitment. Despite the U.S. stance against deploying nuclear weapons in areas targeted by North Korea, the United States is now confronted with the threat of North Korean nuclear capabilities, underscoring the need for the United States to acknowledge the Nuclear Non-Proliferation Treaty’s (NPT) failure and prompt China to reconsider its policies by allowing conditional nuclear weapons development in South Korea and Japan within the context of North Korea’s denuclearization.

Some raise concerns about potential Chinese backlash and retaliation as well as the reinforcement of military cooperation among North Korea, China, and Russia due to this integrated MD system. But South Korea cannot rely solely on goodwill from China and Russia and must actively secure the means to shift its policy position. An “integrated” ROK-U.S.-Japan MD system must be established.

It is crucial to consider the possibility of a situation similar to the 2016 Terminal High Altitude Area Defense (THAAD) deployment in South Korea. In that case, initial ambiguity in the decision-making process quickly turned into a consensus for deployment, escalating tensions with China. Since 2014, the United States had been pushing for the need to deploy THAAD. However, the South Korean government consistently adhered to the position of “No Request, No Consultation, No Decision (3 No’s),” asserting that no requests, discussions, or conclusions had been made concerning THAAD. After North Korea’s fourth nuclear test in January 2016, the Park Geun-Hye administration announced the consideration of a THAAD deployment aligned with security and national interests, leading to subsequent discussions between South Korea and the United States on the matter. While China consistently opposed the THAAD deployment, no official or unofficial consultations between South Korea and China took place on the matter, leading to both countries expressing their respective positions and transforming the THAAD issue from a security concern into an emotional dispute rather than a question of national security.

To prevent the recurrence of such a situation, it is crucial for the integrated MD system to clearly establish from the outset that this is an inevitable choice.  In a 2022 interview with South Korean media, Chinese Ambassador to South Korea Xing Haiming asserted, “THAAD is under the control of the United States … the detection range of THAAD’s X-band radar is 2,000 to 3,000 kilometers. It directly threatens China’s strategic security as it reaches deep into China’s mainland.” South Korea needs to tell China that while we acknowledge China’s anxieties and concerns, South Korea no longer has a choice but to establish an integrated missile defense system to counter North Korean nuclear and missile threats. At the same time, South Korea needs to consult with the United States and Japan about ways to limit the use of detection capabilities against China’s missile forces.

* The views expressed herein do not necessarily reflect the views of the Asan Institute for Policy Studies.

About Experts

Choi Kang
Choi Kang


Dr. CHOI Kang is the President at the Asan Institute for Policy Studies. Previously, he was the dean of Planning and Assessment at the Korean National Diplomatic Academy. In 2012, Dr. Choi served as the president at the Institute of Foreign Affairs and National Security (IFANS). He was also a professor and director general for American Studies at IFANS, a research fellow at the Korea Institute for Defense Analyses, and senior director for Policy Planning and Coordination on the National Security Council Secretariat. He holds several advisory board memberships including: the Committee on Foreign Affairs, Trade, and Unification of the National Assembly; Ministry of National Defense; Ministry of Unification; Air Force Development Committee; and the National Unification Advisory Council. Dr. Choi was also a South Korean delegate to the Four-Party Talks. He writes extensively on the ROK-US alliance, North Korean military affairs, inter-Korean relations, crisis management, and multilateral security cooperation. Dr. Choi received his B.A. from Kyunghee University, M.A. from the University of Wisconsin-Madison, and his Ph.D. in political science from Ohio State University.