The Failure of the 9/19 Comprehensive Military Agreement: What Now?

(Source: Republic of Korea Office of the President. Official Photographer: Kang Min Seok)

In 2018, a historic meeting between South Korean President Moon Jae-in and North Korean leader Kim Jong Un resulted in the Panmunjom Declaration. The subsequent implementation protocol in the military domain, the Comprehensive Military Agreement (CMA), was signed on September 19, 2018. To defuse military tensions and avoid war on the Korean Peninsula, the Democratic People’s Republic of Korea (DPRK or North Korea) and the Republic of Korea (ROK or South Korea) defined zones across land, sea and air based on the Military Demarcation Line (MDL) drawn at the end of the Korean War in 1953. Opinion within the ROK was divided on the CMA’s effectiveness to begin with, and the agreement is now effectively dead.

Since the end of the summit era with North Korea, the ROK and US have worked to increase confidence in US extended deterrence through the establishment of the Nuclear Consultative Group (NCG) and pursuing conventional-nuclear integration (CNI) to deter North Korea’s growing weapons of mass destruction (WMD) capabilities. While these efforts have been a politically significant achievement, they have not been effective in restraining North Korea from engaging in provocative behaviors across multiple domains. For all the flaws and ambiguities that existed within the CMA, its greatest value was in promoting a more stable security environment on the Korean Peninsula. This is unlikely to be replicated any time soon.

Misunderstandings About the 9/19 Comprehensive Military Agreement

While the CMA was presented as a way to defuse tensions between the two Koreas, in reality, many of the provisions overlapped with pre-existing measures, making its purpose more symbolic than practical. The MDL and the Northern Limit Line (NLL) in the West and East Seas were established after the Korean War. Several other limits were subsequently adopted unilaterally by the ROK to avoid direct naval clashes and reduce the chances of South Korean fishing vessels being abducted. In fact, the ROK Navy has frequently conducted multi-layered naval drills and exercises in regions well short of these limit lines, and the only time that the two navies confronted one another was during the Yeonpyeong naval skirmishes of 1999 and 2002.

The CMA supposedly established a military buffer zone, but since the demilitarized zone (DMZ) and the NLL were already fulfilling this role as de facto national boundaries, the CMA is best understood as a rather opaque military agreement between the leaders of the two Koreas, which only acquired significance by overstating the existing situation as a hot war comparable to the Korean War of 1950-1953. This opacity led to repeated claims from the South that the North was violating the CMA: North Korea’s unmanned aerial vehicle (UAV) infiltrations near Seoul, artillery drills in coastal areas and the launch of a reconnaissance satellite known as Malligyong-1 were all seen by the South as breaking the agreement. Meanwhile, the North claimed that all these activities were legitimate responses to US-ROK combined air and naval drills, despite these exercises being conducted far away from the buffer zone stipulated by the CMA.

The CMA was essentially a political agreement between North and South Korea, representing the implementation of the Panmunjom Declaration in the military sphere. However, since the United Nations Command (UNC) is responsible for supervising military confrontations and conflicts between the two Koreas, it was unclear how CMA violations should be dealt with. The CMA mandated maritime peace zones in the West and East Seas, a no-fly zone near the MDL and the dismantling of guard posts near the DMZ, but never addressed the role of the UNC within any of its provisions, how to evaluate practices already in place within those zones or who had jurisdiction in case of violations. On-scene ROK military commanders were often confused about how they could abide by the CMA without changing their combat readiness posture. For example, the NLL in the West Sea is subject to strict Rules of Engagement, self-defensive in character, determined by the United Nations Command (UNC), so the chain of command for CMA violations was unclear.

Furthermore, risk-reduction management, another often stated goal of the CMA, is already part of the 1953 Armistice Agreement, requiring close coordination between the UNC, US Forces Korea (USFK), and ROK/US Combined Forces Command. However, the government of former ROK President Moon tried to limit the role of the UNC regarding the operations of ROK forces in areas designated as buffer zones in the CMA, thus creating a fundamental ambiguity about who was responsible for implementing the Armistice Agreement on the Korean Peninsula. For example, was the UNC still overseeing the Joint Security Area, the NLL and the Han River Estuary, or did the CMA transfer this responsibility to the institutions it established, such as the Joint Inter-Korean Military Committee?

How Can the ROK Manage Conventional-Nuclear Integration Without the CMA?

During 2023, this question about how to manage CNI was the focus of intensive discussions between the ROK and the US. A summit meeting between ROK President Yoon Suk-yeol and US President Joe Biden concluded with the Washington Declaration on April 26, 2023. This established the NCG as the central mechanism for consultation about how the US nuclear umbrella protects South Korea. The US has also raised the visibility of its extended deterrence by sending strategic assets to the Korean Peninsula, and, in effect, the Yoon administration agreed to uphold its obligations under the Nuclear Nonproliferation Treaty by not pursuing an indigenous nuclear capability, at least for the present.

At the latest NCG meeting on December 16, 2023, the CNI concept was proposed. This is intended to mitigate the disparities caused by the unbalanced capabilities between the ROK and the US so that the ROK can deploy its powerful and scalable conventional weapons in support of US extended deterrence by all non-nuclear means. For example, South Korea has recently had a successful test launch of its Hyunmoo-5 missile, which can penetrate underground targets to a depth of 100 meters.

Despite these positive developments within the alliance, the ROK still faces challenges in stopping North Korea’s continued conventional provocations across multiple domains, air and sea especially, but including space and cyber domains as well. The combined defense posture against massed North Korean conventional attacks, including its KN-23 tactical short-range ballistic missiles and super-large artillery, must also be robust against hit-and-run conventional provocations, such as the UAV infiltrations of late 2022.

Political Ramifications of the NCG Mechanism

Since President Yoon took office, getting credible US extended deterrence has been his primary national security goal. Now that the ROK has acquired some input into the operation of US extended deterrence, through the NCG mechanism, there is reason for greater confidence that North Korea’s nuclear and missile programs can be effectively deterred.

Without the CMA, however, and as ROK and US cooperation in conventional-nuclear integration deepens, North Korea is likely to conduct some minor military confrontations near the NLL in the West Sea (Yellow Sea). Kim will doubtless try to play off China against Russia, as Russia-DPRK military cooperation continues to grow.

Moreover, because the US is wrestling with ongoing wars in Europe and the Middle East, as well as potential military crises in Taiwan and the South China Sea, there may come a time when the Biden administration’s attention is too divided to make the Korean Peninsula a priority.

Despite the flaws of the CMA, it still served as a mechanism to help regulate North Korea’s actions toward the ROK. Unfortunately, nothing like it is likely to come around again for the foreseeable future.


The tone of North Korean rhetoric has clearly changed recently, saying that North Koreans should be ready for a great revolutionary event and using phrases that have previously been applied to describe war with South Korea. But surely, the Kim regime understands that it would not survive if it launched any kind of nuclear attack on the ROK, USFK, Japan or Guam. For the time being, however, the threat of conventional attacks must be taken more seriously, though the exaggerated rhetoric is likely aimed mostly at Kim’s domestic audience.

In conclusion, the CMA is now behind us, but US extended deterrence against North Korean nuclear and missile capabilities has been consolidated: the Nuclear Consultative Group is implementing Conventional-Nuclear Integration within the alliance, and the ROK has plausible involvement with decisions taken about the use of the US nuclear arsenal on the Korean Peninsula. While another Korean War seems unlikely, North Korean rhetoric continues to push the envelope. The ROK and the US must, and surely will, continue to prepare for the nightmare scenario.

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