As North Korea fortifies the DMZ, a cease-fire buffer is again becoming a frontline security test

[EXPLAINER]

A narrow strip of land meant to prevent another war on the Korean Peninsula is becoming a renewed source of conflict.

North Korea is fortifying the demilitarized zone (DMZ), installing new roads and infrastructure that could improve the country’s military mobility and operations.

The DMZ is a buffer zone separating the two Koreas, established in 1953 to halt hostilities after the Korean War (1950-53).

North Korea has not only built roads in the DMZ but installed wire entanglements about 80 meters (262 feet) above the military demarcation line (MDL) — the line that separates North and South Korea — according to data shared by the main opposition People Power Party Rep. Kang Dae-sik in June. 

Pyongyang’s efforts come after North Korean leader Kim Jong-un in 2023 declared that the two Koreas are “hostile states” rather than partners seeking reunification. The North’s recent movements also align with Kim’s orders unveiled in May, which include strengthening front line military units. 

Experts believe North Korea's actions are driven by multiple objectives, one of which is preparing for a possible attack on South Korea.

What measures has North Korea taken along the border?

Since late 2023, North Korea has installed new military infrastructure such as roads, wire entanglements and defensive walls along the MDL.

Pyongyang has built about 70 kilometers (43 miles) of tactical roads along the border, according to the South Korean military. Roughly 10 meters (33 feet) wide, the roads are large enough to accommodate military vehicles, facilitating the swift movement of troops and equipment.

North Korea has also constructed defensive walls while clearing land 5 to 10 meters north of the MDL to lay land mines.

The work comes after Pyongyang blew up sections of roads and rail links connecting the two Koreas and declared the South a hostile state, signaling its intention to halt cooperation with Seoul.

What is Pyongyang after? 

In the event of a war, North Korea’s newly built roads can serve as an extra line of defense.

“North Korea has likely built these defensive fortifications in a way that won't get in the way of attacking the South,” Jung Kyeong-woon, a senior research fellow from the Korea Research Institute for Strategy, told the Korea JoongAng Daily. “In contrast, if South Korea counterattacks and moves north, these fortifications could become obstacles in its path.”

The roads can also be the new front line when attacking the South.

"North Korea isn't just building defenses — it is setting things up so it can attack South Korea,” Park Won-gon, a North Korean Studies professor at Ewha Womans University, told the Korea JoongAng Daily. “They are making it possible to strike and invade the South. Basically, they built defenses to stop South Koreans from going north, but they also built tactical roads so they can come down south for a surprise invasion whenever they choose.” 

North Korea has expressed its intention to attack South Korea, while stressing that reunification is not on the table. 

Kim said in January 2024 that in the event of a war, it is “important to reflect on the issue of completely occupying, suppressing and reclaiming [South Korea] and incorporating it” into North Korea. 

As for the mine emplacement above the MDL, it can strengthen North Korea’s defenses during wartime but may serve another strategic purpose.

“Building these defenses won't help much in a military fight, but instead their main purpose would be to prevent North Korean citizens and soldiers from fleeing south,” Jung said.

North Korean nationals, including soldiers, sometimes cross the fortified border to escape, with one civilian having done so on July 3 last year.

What does it mean for border security?

North Korea’s fortifications can put more pressure on South Korean soldiers along the border.

“North Korea’s movement close to the MDL increases the possibility of a surprise attack, meaning we would have less time to react,” Park said. “We therefore need to further strengthen our deterrence and readiness.”

The North has already made several provocations while fortifying the DMZ. A group of North Korean soldiers crossed the MDL in the eastern front line area in April of last year, prompting South Korean troops to fire warning shots and forcing them to head back north.

Seoul, however, has yet to make notable movements in response to the North’s fortifications.

“Beyond monitoring the situation, there will likely be no major response,” Jung said. “Our military can prepare internally for the potential negative military effects, but most of those preparations will likely involve tactical measures. We should avoid actions that could raise tensions and take only the minimum defensive steps necessary when required.” 

The United Nations Command (UNC), meanwhile, maintains that North Korea's recent movements are not violations of the 1953 Armistice Agreement — the agreement establishing the cease-fire and the DMZ — as they remain "north of the MDL and do not introduce heavy weaponry." 

"Construction of fences and roads is permitted if it remains north of the MDL," a fact sheet released by the UNC on June 23 said. "Fences serve a defensive, separation purpose. Emplacing mines defensively on the northern side is permitted." 

What approach is South Korea taking?

While North Korea is focusing on fortifying the border, South Korea has shifted to a different approach to maintaining border security.

The Ministry of National Defense said in April that it would gradually reduce the number of troops stationed at general outposts near the border from the current 22,000 to 6,000 by 2040 and replace them with AI-equipped surveillance systems.

The Defense Ministry’s position is that the plan is not intended to weaken front line readiness, but to make border patrol operations more efficient and technology-driven in the era of population decline.

“Our reduction of front line guard personnel is not related to North Korea’s recent efforts to fortify its front line areas,” Jung said. “South Korea can gradually reduce the number of front line guard troops because the population and military manpower are declining, border security systems are becoming more advanced and rear units need to maintain their combat readiness.

“The main purpose of guard units is to prevent enemy infiltration. However, the possibility and need for North Korea to carry out a ground infiltration have decreased significantly. Therefore, maintaining only the minimum number of guard troops is the appropriate choice for South Korea.”

But if North Korean soldiers outnumber South Korean forces along the front line during wartime, it could give the North an edge.

“In a war, looking at past conflicts, we would likely see a large-scale ground battle involving armored units and a large number of troops,” Park said. “Even though we would use air and naval forces to strike North Korea, the fighting would still take place on the ground, making the number of ground troops very important. Also, as shown in the Russia-Ukraine war, drones are becoming an important part of ground warfare. So, unless a nuclear war breaks out, the number of troops will still matter in a ground conflict, and this remains a concern for South Korea.”

More troops or fortifications near the border may not directly translate into better military capabilities. North Korea’s recent moves, however, are a sign that Pyongyang has no intention of backing down militarily.   

With North Korea’s continued efforts, South Korea faces the challenge of responding to the moves across the border while seeking a breakthrough in inter-Korean relations.

BY PAIK JI-HWAN [paik.jihwan@joongang.co.kr]