North Korea made headlines last week by pledging to activate its loudspeaker systems to broadcast its propaganda to the South, but the latest dispute comes amid Kim Jong-un’s years-long border militarization.
Since April 2024, North Korea has been working to build a permanent fortified border across the demilitarized zone (DMZ) that divides the two sides, work that led to a mine explosion that injured three South Korean soldiers and plunged ties to new lows.
Here’s a brief guide to what’s being built, what Pyongyang claims it’s for, and why even deciding where the border is has become such a delicate issue.
What is North Korea building on the border?
The 250 km border is already fortified, but not in the way many might traditionally think. For the moment it is more of a buffer than a barrier, in the form of a 4 km wide demilitarized zone (DMZ) which crosses the Korean peninsula.
Since 2024, the North has reportedly laid around 960,000 mines in the DMZ, nearly half of all mines believed to be in an area that is already one of the most mined areas on the planet.
North Korea has also constructed a continuous physical barrier on its side of the area, along the entire length of the line. It is made up of fences, minefields, tactical roads and anti-tank barriers placed on ground devoid of vegetation. South Korea’s Joint Chiefs of Staff say the clearing is almost complete while construction work is 40-60% complete, and expects it to be finished by the second half of 2028.
Under the 1953 armistice that ended but did not end the Korean War, the DMZ was to be cleared of military forces and equipment.
Why is Kim Jong-un doing this?
Kim Jong-un has abandoned the once cherished goal of reunification. As recently as 2018, leaders from both sides met at the border and their athletes marched together in the Winter Olympics. But in December 2023, Kim redefined the South as a separate, hostile state, and construction began a few months later.
Experts in Seoul say Kim’s change of heart has eliminated the contradiction that lay in the threat of nuclear war against a people the North once called compatriots. When relations with Seoul collapsed and Moscow became a boss, Pyongyang was left free to push for recognition as a nuclear state.
They also say the construction achieves several goals: preventing North Koreans from leaving, slowing any South Korean advances in the event of a return to war, and transforming the border into something that functions as an international border.
Kim Yo-jong, the North Korean leader’s powerful sister, said the work would eliminate the danger of border conflict. However, analysts argue the opposite: that the new artillery and missile units being installed make an accidental clash more likely to escalate.
Why are tensions rising now?
On September 21, three South Korean soldiers were injured by a landmine explosion while fighting their way inside the DMZ. A soldier lost his foot.
The South Korean military concluded that the explosion was caused by a North Korean mine placed south of the border, and Seoul demanded an apology. Pyongyang has denied responsibility for the incident and called it a “self-organized prank.”
South Korea says North Korean troops crossed the border several times during work to fortify their side of the line, leading to warning shots that Pyongyang says are provocations by “armed thieves.”
Kim Yo-jong has since issued a dozen statements in less than a month criticizing the South, a frequency that Seoul’s Unification Ministry called unusual. She recently said the North’s propaganda loudspeakers would be ready to cross the border within days.
Does anyone know where the border actually runs?
The Armistice drew the Military Demarcation Line (MDL) on maps at a scale of 1:50,000, where a line just a millimeter wide covers about 50 meters of land. In total, 1,292 numbered markers were then planted to fix it, but only around 200 are still identifiable.
Everyone therefore reconstructed it according to their own methodology. Seoul works from mapping aligned with that of the US National Geospatial-Intelligence Agency, while the US-led UN Command (UNC), which oversees the armistice, uses its own survey from a decade ago. It is believed that North Korea is simply connecting the markers it can still see. South Korea’s Defense Ministry found that its line and that of the UNC disagreed on about 60 percent of the points they compared, in places by tens of meters. It is unclear to what extent the two Koreas interpret this line differently.
North Korean troops reportedly crossed the border around 50 times in August and September this year alone, compared to 17 times in 2025.
Is anything being done to resolve the border issue?
Seoul tries. He proposed talks to jointly confirm where the MDL circulates, restore cut military communications channels in 2023 and agree on ways to avoid accidental clashes. This is the second such offer in a year. Pyongyang ignored the first.
The South Korean Defense Ministry calls the work a violation of the armistice and has demanded it be stopped. The UNC, for its part, said that construction and fortification do not automatically constitute violations and that each case must be judged according to the facts.
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