Why We Must Proactively Restore the September 19 Military Agreement
Yong-geun Cho
Former Director of North Korea Policy
Ministry of National Defense
The Demilitarized Zone (DMZ), a critical buffer zone underpinning security on the Korean Peninsula, is once again experiencing heightened tensions. At the Ninth Plenary Meeting of the Eighth Central Committee of the Workers’ Party of Korea, held in late December 2023, Kim Jong-un defined inter-Korean relations as “relations between two hostile states, not between fellow Koreans.” He explicitly designated South Korea as the “number one hostile country” and the “unchanging principal enemy,” calling for the abandonment of the existing concepts of peaceful reunification and “fellow Koreans” and directing that this policy shift be reflected in the Constitution.
Subsequently, at the Ninth Party Congress in February 2026, Kim emphasized the need to “fortify the southern border adjacent to South Korea as soon as possible and reinforce the border defense and firepower systems.” North Korea’s amended Constitution has since incorporated territorial provisions consistent with this policy. In fact, since 2024, the North Korean military has been constructing a new “border line” along the Military Demarcation Line (MDL) within the DMZ. South Korea’s Joint Chiefs of Staff estimates that the construction will be completed within two to three years.
The central concern with North Korea’s designation of the MDL as a border is that, once its military border patrols become fully operational, the risk of armed clashes between the two Koreas could become structural and recurring. This is largely because the two militaries have different understandings of the MDL’s precise location within the DMZ.
When the 1953 Armistice Agreement was signed, the two sides agreed to mark and manage the MDL using 1,292 boundary markers. However, following the inter-Korean armed clashes of the 1970s, these markers were neglected, damaged, or lost, and only approximately 180 remain today. Even those that remain have been displaced by natural disasters and other factors, making it difficult to determine the MDL’s precise location. In some cases, the reference lines used by the North and South Korean militaries differ by tens of meters. The possibility that such relatively minor discrepancies could escalate into armed clashes has therefore become a persistent concern.
In particular, once North Korea completes its border construction, the two-kilometer-wide northern half of the DMZ—the buffer zone established under the Armistice Agreement—will effectively cease to function. Regardless of the legal validity of North Korea’s actions under international law, this would mean that the DMZ, which has served as the Korean Peninsula’s minimum security safeguard for more than 70 years, would lose much of its practical effectiveness.
This situation did not emerge overnight. As the Yoon Suk-yeol administration adopted a more confrontational approach toward North Korea, the two Koreas ultimately suspended and effectively dismantled the September 19 Military Agreement. Since then, guard posts (GPs) that had been withdrawn from the DMZ have been reestablished, and North Korea has erected a barrier near the MDL. Both militaries have resumed artillery fire in areas surrounding the Northern Limit Line (NLL) in the West Sea, while North Korea has demolished the inter-Korean connecting roads along the Donghae and Gyeongui lines.
Drone incursions into each other’s airspace over the respective capitals, South Korea’s distribution of leaflets targeting North Korea, and North Korea’s release of balloons carrying waste have further compounded tensions. Military tensions along the border have consequently risen to exceptionally high levels.
Against this backdrop, North Korea’s current efforts to fortify the MDL can be understood as an attempt to undermine the existing armistice system. The breakdown of the September 19 Military Agreement was a critical turning point in the deterioration of the security environment.
Preventing the Normalization of Structural Military Conflict
In addressing the current crisis on the Korean Peninsula, our foremost concern should be the “normalization of structural military conflict.” If South Korea’s military consistently adopts a hard-line response and treats North Korea’s construction of a border line solely as a military provocation, there is a significant risk that an unintended or accidental armed clash could escalate into a full-scale local conflict. This risk is particularly acute as North Korea intensifies its hostility toward the South under its “two hostile states” doctrine. Any military confrontation between the two Koreas could therefore escalate to a level unprecedented in previous inter-Korean crises.
The South Korean government must consequently develop a precise and comprehensive response strategy. Its most urgent responsibility is to fill the void left by the erosion of the existing armistice system—not with the prospect of armed conflict, but with an institutionalized framework for peace.
This ultimately requires the proactive restoration of the September 19 Military Agreement. South Korean President Lee Jae-myung has already expressed his commitment to restoring the agreement in phases, both in his August 15, 2025, commemorative address and at a press conference earlier this year. Accordingly, the government should pursue a two-track approach to proactively restoring the agreement: flexibly applying the South Korean military’s warning-fire criteria to routine North Korean border patrol activities in order to reduce the risk of accidental clashes, while responding firmly and proportionately to deliberate provocations.
What the September 19 Military Agreement Demonstrated
The September 19 Military Agreement, signed in 2018, represents a significant example of arms control on the Korean Peninsula and was the first agreement of its kind to be implemented by the South and North Korean militaries. In practical terms, it was also the only agreement between the two military authorities that remained operational until its suspension and subsequent breakdown.
The agreement did not emerge in isolation. It carried forward the principles of ending hostilities and pursuing a peaceful resolution established in the 1953 Armistice Agreement. It also represented the culmination of decades of inter-Korean engagement and arms-control efforts under successive South Korean administrations—from the Inter-Korean Basic Agreement and the Non-Aggression Supplementary Agreement under the Roh Tae-woo and Kim Young-sam administrations, to the June 15 Joint Declaration and the October 4 Declaration under the Kim Dae-jung and Roh Moo-hyun administrations, as well as arms-control initiatives pursued under the Lee Myung-bak and Park Geun-hye administrations.
The agreement’s achievements were substantial. On land, it established a 10-kilometer-wide buffer zone extending five kilometers on either side of the MDL, bringing an end to artillery fire and field exercises involving units at the regimental level or above. In the maritime areas surrounding the NLL in the West and East Seas, it established buffer zones that halted naval and coastal artillery firing. It also designated no-fly zones for specified types of aircraft over the MDL, effectively prohibiting flights that had not been notified in advance.
In particular, at the Joint Security Area (JSA) in Panmunjom, South Korea, North Korea, and the United Nations Command (UNC) conducted a joint on-site verification—the first of its kind since the signing of the Armistice Agreement—and completed the demilitarization of the area. This helped create the conditions for a summit among the leaders of South Korea, North Korea, and the United States to take place at Panmunjom just over 30 hours after President Donald Trump unexpectedly proposed a meeting with Kim Jong-un in June 2019.
The pilot withdrawal of 22 GPs in areas where the risk of mutual confrontation was particularly high was recognized by the United Nations as a notable example of conventional arms control. The joint inter-Korean recovery of remains at Arrowhead Hill and White Horse Hill also represented a symbolic effort to address the enduring human and historical costs of the Korean War. The fact that only a very limited number of violations were confirmed following the agreement’s implementation demonstrates its effectiveness as a mechanism for reducing military tensions. In particular, the agreement established verification procedures for monitoring implementation, creating a historical precedent in which South and North Korean military personnel crossed the MDL into each other’s territory to directly inspect military facilities.
A Core Element of the Korean Peninsula’s Peace Regime and a Framework That Must Evolve
The significance of the September 19 Military Agreement extends beyond its immediate contribution to reducing military tensions. It also provides a starting point for establishing the core elements of a peace regime on the Korean Peninsula. If the concept of a peace regime seems abstract, it becomes more tangible when considered in terms of the provisions that a future peace treaty would need to contain. Such a treaty should establish a vision for future political relations between North and South Korea, rules and norms governing economic and social exchanges, a framework for achieving the complete denuclearization of the Korean Peninsula, and, above all, a military order designed to ensure that war never occurs again.
An examination of these elements reveals that considerable groundwork has already been laid between the two Koreas. The 1991 Inter-Korean Basic Agreement encompasses fundamental principles governing political and economic relations, while detailed norms and practices for economic and social exchanges have been developed over the years. The vision for denuclearization is also clearly articulated in the 1992 Joint Declaration on the Denuclearization of the Korean Peninsula.
Military affairs, however, remain insufficiently developed. Although the Inter-Korean Basic Agreement and subsequent declarations established important principles, their provisions were too general to effectively regulate actual military activities. Moreover, the Inter-Korean Joint Military Committee envisaged in the Basic Agreement never advanced to substantive discussions of specific military issues. Subsequent initiatives, including the October 4 Declaration, likewise failed to produce the intended results.
Against this backdrop, the September 19 Military Agreement is particularly significant because, building on the Armistice Agreement and the Inter-Korean Basic Agreement, it established substantive and operational arms-control provisions for the first time. These provisions included concrete confidence-building measures such as the joint recovery of war remains, the withdrawal of GPs, the demilitarization of the JSA, and the removal of loudspeakers.
It is important to recognize, however, that the agreement was not intended to constitute a final settlement. Rather, it established a framework designed to evolve over time, with the Inter-Korean Joint Military Committee serving as the institutional mechanism for advancing that process. The committee’s establishment would not resolve every outstanding issue immediately. It would, however, provide an opportunity for the military authorities of both Koreas to place their respective concerns on the table and begin substantive dialogue through frank and open exchanges.
Assessments of the September 19 Military Agreement remain divided between those who evaluate it in terms of its overall benefits and those who focus on the distribution of relative gains. Both perspectives have merit. Although the distribution of relative gains is undoubtedly important in international politics, an excessive focus on scrutinizing every aspect of how the benefits of a negotiated agreement are distributed can provoke the other party and undermine the very outcome the negotiations were intended to achieve.
What is clear is that the agreement reduced military tensions in border areas and helped create conditions that enabled the two Koreas and the United States to focus on negotiations toward a peace regime on the Korean Peninsula. The September 19 Military Agreement was not the culmination of inter-Korean arms control, but its first substantive step. We must now pursue the longer and more difficult process of building on the framework it established.
This approach is consistent with the vision President Lee Jae-myung outlined in his August 15 commemorative address this year. Referring to “stable peaceful coexistence without the need for conflict,” President Lee expressed his commitment to establishing mechanisms for managing tensions and conflicts, developing multiple safeguards to prevent crises from escalating, and taking proactive and sustained measures to reduce military tensions in border areas. He also outlined a path toward transforming the unstable armistice regime into a peace regime and called on both Koreas to set aside their intentions to threaten one another and begin direct dialogue.
For this policy direction to produce tangible results, the September 19 Military Agreement must ultimately be restored and further developed. Beginning with this agreement, South and North Korea share the responsibility of steadily building the institutional foundations for lasting peace on the Korean Peninsula.
Conclusion: The Starting Point of a Bold Journey
With the breakdown of the September 19 Military Agreement, military tensions in border areas have once again reached exceptionally high levels, creating conditions in which an accidental armed clash could occur at any time. Paradoxically, this situation underscores how effectively the agreement had served as a safeguard against military confrontation and how it opened a new chapter in arms control on the Korean Peninsula. It also highlights the agreement’s role in creating conditions conducive to denuclearization and establishing a core element of a future peace regime.
North Korea’s efforts to turn the MDL into a border line and thereby undermine the practical effectiveness of the armistice system further demonstrate the need to establish a new peace regime. Rather than simply returning to the status quo ante, we should use the restoration of the September 19 Military Agreement as a springboard for a bold and sustained effort to conclude a peace treaty on the Korean Peninsula, advance phased denuclearization, and establish an enduring arms-control regime.
In particular, amid rapidly evolving international dynamics, including the U.S.-China summit, the parallel use of more ambitious and substantive diplomatic incentives will be essential to bringing North Korea back to the negotiating table for a U.S.-North Korea summit.
Throughout this process, the role of the military authorities on both sides will become increasingly important, alongside decisions by their respective leaders and negotiations conducted through diplomatic channels. Above all, public support and trust, together with the backing of the international community, will be essential for enabling the South Korean military to restore and further develop the September 19 Military Agreement.
The establishment of lasting peace between the two Koreas ultimately depends on whether military tensions in border areas can be reduced. The resumption of the Korean Peninsula peace process, including renewed inter-Korean and U.S.-North Korea engagement, must begin here. What is needed now is not another new vision, but the political will and courage of South Korea and the international community to restore agreements whose practical value has already been demonstrated.