North Korea's border fortification raises questions over DMZ buffer role
North Korean troops lay mines in the Demilitarized Zone along the central front, June 18, 2024. The Joint Chiefs of Staff (JCS) said dozens of North Korean soldiers working in the area crossed the Military Demarcation Line before retreating after South Korean troops issued warning broadcasts and fired warning shots. Courtesy of JCS
Minefields, barriers and unclear MDL raise risks of accidental clashes
North Korea’s continued construction of minefields, fences and barriers along the Military Demarcation Line (MDL) is raising questions over whether its border fortification campaign is changing the role of the Demilitarized Zone (DMZ), which has served as a military buffer between the two Koreas since the 1953 Korean Armistice Agreement.
The risks are becoming more apparent as North Korea builds fortifications close to the MDL in areas where Seoul, Pyongyang and the United Nations Command (UNC) do not always agree on the exact location of the line.
North Korean troops have repeatedly crossed the MDL during construction work, prompting warning broadcasts and warning shots from the South Korean military.
North Korea began clearing land, laying mines and building fences, barriers and tactical roads along the MDL in 2024, after leader Kim Jong-un defined inter-Korean relations as those between “two hostile states.”
The South Korean military expects the project to be completed around 2028. As of August, land-clearing work was about 90 percent complete, while construction of fences and minefields was estimated to be 30 to 60 percent complete, depending on the area.
Yoo Ji-hoon, a research fellow at the Korea Institute for Defense Analyses, said the fortification campaign could change the military character of the DMZ even if its formal boundaries remain unchanged.
“If North Korea places military facilities such as fences, minefields and tactical roads excessively close to the MDL, the practical military buffer space could effectively shrink even if the physical width of the DMZ itself remains unchanged,” Yoo said.
Shin Jong-woo, secretary-general of the Korea Defense and Security Forum, noted that the DMZ, which extends 2 kilometers on each side of the MDL, has served as a buffer to prevent clashes, but the North’s construction of tactical roads, fences, barriers and minefields inside could weaken that function.
“North Korea’s so-called border fortification work is ongoing,” a Joint Chiefs of Staff (JCS) official said Friday.
Defense Minister Kang Shin-chul has linked a recent mine explosion in the DMZ to the fortification work. Speaking at the National Assembly on Tuesday, Kang said a North Korean mine found near the blast site appeared to have been planted rather than washed into the area, adding that it was believed to have been laid “in connection with the border fortification.”
Unification Minister Chung Dong-young answers questions from reporters as he arrives at Government Complex Seoul, Friday, after cutting short a trip to Europe following a North Korean mine explosion in the Demilitarized Zone. Yonhap
The DMZ, however, was already heavily mined long before North Korea began its latest fortification campaign. According to JCS data submitted to the National Assembly in 2020, an estimated 380,000 mines were buried within the DMZ, part of some 828,000 mines estimated to remain across South Korea, including locations near the Civilian Control Line and rear areas.
The figures were estimates as of 2020 and do not represent the exact number of mines currently remaining.
South Korean forces also laid mines after the armistice agreement was signed to prevent North Korean infiltration and protect key military facilities. But a JCS official told The Korea Times that South Korea has not carried out new mine-laying or similar fortification work in the DMZ in response to the North’s latest campaign, distinguishing the current situation from minefields laid decades ago.
One complication is that the MDL is no longer clearly marked across much of its 248-kilometer-boundary.
A total of 1,292 markers were originally installed to identify the MDL after the armistice agreement was signed. The defense ministry confirmed Friday that only about 250 remain. South Korea and the UNC have developed their own reference lines based on armistice maps, surviving markers and terrain, but their assessments do not match in some areas.
North Korea, meanwhile, refers to the boundary as its “border.” Kim Yo-jong, the powerful sister of the North Korean leader, denied that North Korean troops had crossed it.
“Our soldiers have never crossed the border even once,” she said Tuesday. Pyongyang has not publicly specified exactly where it considers that border to be.
According to the Defense Intelligence Agency, North Korean troops were assessed to have crossed the MDL about 20 times in August and about 30 times in September.
A JCS official said North Korean troops have sometimes returned with maps and binoculars after receiving South Korean warnings and checked their location before resuming work. In some cases, they moved their work site.
Those risks became apparent on Sept. 21, when a mine explosion in the western DMZ injured three South Korean soldiers. A subsequent investigation found an additional North Korean anti-personnel mine south of the MDL, which the UNC determined constituted an armistice agreement violation.
The South Korean military is also strengthening surveillance in areas where terrain limits visibility. “Additional surveillance equipment is being installed or planned,” a JCS official said, declining to disclose locations for operational security reasons.
Unification Minister Chung Dong-young on Friday proposed talks with North Korea to clarify the MDL.
“We need to meet and communicate,” Chung said. “At the very least, we should begin talks to reconfirm and clearly establish the MDL.”
A defense ministry official said Seoul has “consistently acknowledged differences in how the MDL is understood and the need for consultations,” noting continuing discussions with the UNC.