It was belatedly confirmed on Monday that South Korea’s military and the United Nations Command have been operating under different standards for the Military Demarcation Line (MDL) for several years.
Military sources report that when North Korean forces violate the MDL, United States Forces Korea reviews both U.S. military maps and the UN Command’s reference line and responds based on the southernmost line of the two. This protocol was incorporated into the military’s boundary guidelines last September.
The U.S. military has used maps measuring MDL marker locations based on 2004 data since 2011. The UN Command finalized its reference line in 2016, using measurements from 2014-2015. Currently, the two maps show discrepancies in about 60% of MDL locations, with some areas differing by several dozen meters.
A military official disclosed that the directive to use the southernmost line between U.S. military maps and the UN Command’s reference line for MDL breach determinations was disseminated last June through official channels and briefings to key personnel.
In areas where the UN Command’s MDL is south of the U.S. military’s, responding to North Korean breaches with warning shots could potentially lead to UN Command accusations of armistice violations, potentially straining U.S.-South Korea coordination on North Korea issues.
While the military hasn’t detailed specific problems arising from these MDL discrepancies, sources indicate that North Korea’s own inaccurate MDL recognition has prevented major issues so far.
However, North Korea’s recent disconnection operations near the MDL have required more precise boundary identification, prompting discussions between South Korea and the United States on response protocols.
Military authorities reported 17 North Korean MDL breaches this year, most of them accidental and occurring during disconnection work. Following North Korea’s scrapping of the September 19 inter-Korean military agreement in November 2023 and its December declaration of the two Koreas, the North has been installing barriers and laying mines along the border.
The MDL is marked by limited signage, with only about 200 markers remaining, making on-site identification of breaches difficult without specialized equipment. Of the 17 breaches this year, 11 occurred in November alone. The Defense Ministry proposed talks last month to redefine MDL boundaries, but North Korea has not responded.
U.S. forces respond to North Korean MDL approaches or violations with warning broadcasts and warning shots. The Joint Chiefs of Staff said more than 2,400 warning broadcasts and 21 warning shots have been carried out since last April in response to North Korean MDL breaches.
The Defense Department and the UN Command plan to discuss aligning their MDL reference lines next year, acknowledging the need to bridge their differences.
A Joint Chiefs spokesperson said that to ensure decisive responses to armistice violations in the Demilitarized Zone and prevent accidental clashes, the military has prioritized the use of identifiable MDL markers since last year. Where markers are absent, the spokesperson said, assessments are conducted comprehensively using military maps and UN Command marker coordinates.