To keep the peace, South Korea’s Lee must prepare for war

When a South Korean soldier stepped on a land mine in the Demilitarized Zone (DMZ) on September 21, it might have been taken as a grim reminder of a war that never formally ended. Instead, the explosion has revealed something more unsettling: the Korean Peninsula’s old security order is shifting, even as Seoul tries to revive dialogue with Pyongyang. A joint investigation by South Korea and the United Nations Command found evidence pointing to a North Korean anti-personnel mine near the site of the explosion, which injured three South Korean soldiers, two seriously. Seoul says the mine was planted south of the Military Demarcation Line, in violation of the 1953 Armistice Agreement. North Korea has denied responsibility and accused Seoul of fabricating the incident. The timing is awkward for President Lee Jae Myung, who has been trying to steer South Korea away from confrontation and toward what he has called “peaceful coexistence.” Lee has proposed dialogue, renewed military confidence-building measures and a phased approach to reducing North Korea’s nuclear and missile capabilities. Yet his government is also speeding up military modernization, including a program to build nuclear-powered attack submarines. The two tracks are not necessarily at odds. Rather, they reflect a paradox where the pursuit of peace increasingly depends on the ability to deter war. Peace through deterrence Lee’s approach is more than a softer version of his predecessors’ strategies. It rests on the premise that the two Koreas must find a way to coexist even though Pyongyang has abandoned the old framework of eventual unification and now describes the South as a hostile state. In September, Lee again pledged to pursue peaceful coexistence through dialogue backed by “firm deterrence.” At the United Nations, he proposed respecting North Korea’s political system and sovereignty while seeking a gradual reduction of its nuclear and missile capabilities. The aim is to open enough political space for engagement without abandoning the longstanding goal of Pyongyang’s denuclearization. But that approach makes strategic sense only if diplomacy has credible force behind it. The recent DMZ mine explosion underscores the strategy’s inherent risk. Lee can choose restraint to preserve room for diplomacy, but if Pyongyang reads that restraint as weakness or lack of resolve, it can erode the deterrence that makes future diplomacy possible. North Korea has spent the past several years hardening its border. It has laid mines, built barriers and tactical roads, expanded fencing and repeatedly moved troops across areas close to the Military Demarcation Line. The measures reflect Pyongyang’s somewhat new decision to treat the South not as a temporarily divided compatriot but as a separate, hostile state. The result is a more dangerous border, even if North Korea has no intention of launching a full-scale war. When heavily armed forces operate in close proximity, the greatest danger may not be a deliberate invasion or assault. Rather, the greater risk can be a chain reaction: a mine, a patrol, a warning shot, a retaliation and then a political demand for an even tougher response. South Korea’s demand on September 30 that North Korea halt its border fortification activities shows how quickly this dynamic can escalate. The price of diplomacy The deeper problem lies beyond the DMZ. North Korea is changing the military balance in ways that make conventional deterrence increasingly complicated. North Korea’s artillery has traditionally relied heavily on massed firepower. But the military is now putting greater emphasis on range, precision and the ability to strike deep behind an adversary’s operational lines. A recent test of an extended-range 240-millimeter modular rocket system, which North Korean state media claimed could reach roughly 100 to 115 kilometers, points to a force designed not merely to bombard the front line but to disrupt the movement of reinforcements behind it. In a war, South Korean front-line units are expected to hold off an attack while additional forces mobilize. Precision strikes on roads, chokepoints and supply lines could isolate those troops before reinforcements arrive. Ukraine offers a relevant battlefield lesson: unmanned systems and precision fire can turn exposed terrain and concentrated forces into costly targets. North Korea does not need to conquer the South to gain political leverage. A limited military success, paired with the ability to make a South Korean counterattack prohibitively expensive, could generate pressure for negotiations on Pyongyang’s terms. Nothing here suggests war is imminent, but military modernization, not least the introduction of drone warfare at scale, is changing the options available to both sides. To be sure, South Korea is adapting. The clearest example is its nuclear-powered submarine program. On Sept. 29, Lee’s Cabinet approved a special bill creating the legal and regulatory framework to introduce and operate such vessels. The government aims to begin building the lead submarine in the mid-2030s and to field a domestically built boat later that decade. A nuclear-powered submarine is not a nuclear-armed one. Its reactor provides propulsion and does not automatically turn the vessel into a platform for nuclear weapons. But the strategic implications are significant. A nuclear-powered submarine can stay submerged longer, operate farther from port, track hostile submarines more effectively and survive better in a crisis. That matters for South Korea because North Korea is also developing sea-based nuclear capabilities. Seoul has not answered by seeking nuclear weapons, yet. Instead, it is acquiring more sophisticated conventional deterrence, including technology that depends on nuclear propulsion. That will require closer coordination with Washington on nuclear fuel, technology and nonproliferation arrangements. It also makes the US-South Korean alliance more central to Seoul’s military strategy, even as ties have frayed on multiple fronts under Donald Trump. Seoul is strengthening its deterrent not to abandon diplomacy but to keep diplomacy credible. Yet every improvement in South Korea’s deterrent can give Pyongyang another reason to bolster its own, spurring on strategic escalation rather than stability. That is the classic security dilemma wherein each side can regard its own actions as defensive while reading the other’s as preparation for aggression. What peace now means The biggest obstacle to Lee’s strategy may be less a lack of diplomacy than a disagreement over its purpose. For Seoul, dialogue remains tied to eventual denuclearization. For Pyongyang, that premise is increasingly unacceptable. North Korea’s vice foreign minister, Kim Son Gyong, told the U.N. General Assembly in September that the country’s nuclear status was permanent and irreversible. North Korean Foreign Minister Choe Son Hui has similarly rejected international calls for denuclearization while Pyongyang continues to describe itself as a responsible nuclear-armed state. Seoul wants a peaceful coexistence that eventually creates conditions for denuclearization. Pyongyang increasingly wants coexistence without giving up its nuclear status. Washington faces a similar bind. US President Donald Trump has signaled interest in renewed engagement with North Korean leader Kim Jong Un, while the United States, South Korea and Japan formally continue to advocate for North Korea’s complete denuclearization. The question, then, is no longer simply whether diplomacy can return to the Korean Peninsula, but rather what it would negotiate if Pyongyang refuses to make denuclearization the starting point. Diplomacy need not begin with the elimination of North Korea’s nuclear arsenal. Arms control, crisis communication, military confidence-building, limits on certain deployments and mechanisms to prevent accidental escalation could reduce risks even while the larger dispute over denuclearization remains unresolved. Such an approach would not legitimize North Korea’s nuclear status. It would reflect the fact that refusing to discuss risk reduction until denuclearization occurs may trap both sides in an increasingly dangerous cycle of deterrence and counter-deterrence. That is where Lee’s peace policy will be tested. Lee’s challenge is less about choosing between preparing for war and pursuing peace than about keeping preparation for war from becoming an end in itself. Deterrence has to create room for diplomacy, not replace it. At the same time, diplomacy must reduce the incentives for military escalation without weakening the defenses that prevent and guard against Pyongyang’s coercion. The Korean Peninsula needs a new definition of peace, one that does not mean merely the absence of shooting or an indefinite wait for one side to give up capabilities it considers essential to its survival. The real test for Seoul is whether it can maintain enough deterrence to make Pyongyang’s aggression unattractive, enough diplomacy to make compromise possible and enough restraint to keep the security dilemma from becoming self-fulfilling. For South Korea, preparing for war is increasingly the price of keeping peace possible. Ronny P Sasmita is senior international affairs analyst at the Indonesia Strategic and Economic Action Institution, a Jakarta-based think tank. He holds a PhD from the University of Tokyo.