North Korea’s expanding nuclear arsenal is changing more than just the amount of destruction Pyongyang could inflict. This may be altering the North Korean leadership’s way of calculating how it could use nuclear weapons in a limited conflict while not necessarily triggering regime change. North Korea is developing a larger and more diversified nuclear inventory, tactical nuclear warheads, solid-fuel intercontinental ballistic missiles (ICBM), multiple independently targetable re-entry vehicles (MIRV), cruise missiles, and hypersonic weapons systems. Moreover, North Korea’s September 2022 nuclear law established the conditions under which nuclear weapons may be used preemptively. 

These developments would become particularly perilous when paired with uncertainty regarding how the United States would respond to North Korea’s limited use of nuclear weapons and a simultaneous dual contingency involving China and North Korea. Consequently, the central challenge facing South Korea extends beyond deterring an all-out nuclear attack. It must also ensure Pyongyang does not conclude that limited nuclear use is controllable, survivable, or politically successful. 

A larger nuclear inventory affords greater operational flexibility to North Korea. While a small nuclear stockpile would have to be preserved for regime survival and strategic retaliation, a much larger arsenal would enable Pyongyang to allocate a subset of warheads to American targets, others to Japan, and still others to South Korean military targets. North Korea could reach the tipping point when Kim Jong-un believes he possesses sufficient nuclear capacity to use them for tactical purposes while preserving a survivable nuclear reserve to deter further escalation. 

To achieve doctrinal legitimacy for early use of nuclear weapons, North Korea’s 2022 nuclear doctrine authorizes the use of nuclear weapons not only in response to a nuclear attack but also when the leadership, nuclear command structure, or valuable strategic targets are threatened. Pyongyang could argue that a South Korean attack against its missile bases, command centers, and underground facilities is an attempt to neutralize North Korea’s nuclear deterrent. In that case, a tactical nuclear strike could be portrayed as a defensive measure to halt allied operations and terminate Western aggression. 

This creates a dangerous interaction with South Korea’s Three-Axis System. The Kill Chain is intended to destroy North Korean launchers and command facilities before missiles are fired. Korean Air and Missile Defense (KAMD) is intended to intercept the remaining missiles, and Korea Massive Punishment and Retaliation (KMPR) is intended to pose a threat to the North Korean leadership. From Pyongyang’s perspective, these strikes may be interpreted as an integrated operation aimed at destroying North Korea’s nuclear forces and decapitating its leadership. Ironically, increased South Korean preemptive-strike capability may result in  greater North Korea’s incentive to disperse authority, shorten decision times, and launch its forces before they could be destroyed. 

North Korea’s lessons learned from the Russo-Ukrainian war could make this posture even more dangerous. Russia has repeatedly combined or integrated drones, cruise missiles, and ballistic missiles with other measures. North Korea could apply similar methods on the Korean Peninsula. Beginning with cyberattacks and GPS jamming, followed by reconnaissance drones toward missile-defense batteries, airfields, ports, and command centers. An additional wave could include decoys, one-way attack drones, low-altitude cruise missiles, ballistic missiles including KN-23 and KN-24, and hypersonic systems. 

Nuclear-tipped missiles could be mixed with conventionally armed weapons to generate attack uncertainty like a “haystack attack.” South Korean operators might not be able to discern which incoming objects are decoys, which carry conventional warheads, and which are armed with nuclear warheads. As a result, Seoul would be compelled to consume their stock of interceptors against numerous targets. North Korea does not need hundreds of drones to neutralize the KAMD. It would instead need drones that could damage radar, communications vehicles, generators, reloading systems, or command hubs long enough for ballistic missiles to penetrate successfully. 

The Atlantic Council’s Guardian Tiger tabletop exercises explicitly revealed this problem. In one scenario, North Korea employed a low-yield nuclear weapon against ROK Navy facilities. In response, the United States chose to conduct strong conventional strike operations instead of opting for nuclear retaliation, partially because of concerns about escalation with China. 

These risks could be amplified during a Taiwan conflict with American military assets heavily deployed in the Taiwan Strait. Under such circumstances, North Korea could use mobilization, missile attacks, or tactical nuclear blackmail either to coerce the United States into dispersing its assets or to restrict Seoul’s support for Taiwan operations. Meanwhile, China might disapprove of North Korea’s use of nuclear weapons but still intervene to forestall regime collapse.  

South Korea should respond by denying North Korea confidence in such a strategy. In that regard, the following six recommendations are worth pursuing, either individually or collectively. 

First, the Three-Axis System should be operated as a continuously functioning, integrated architecture instead of three mutually separated stages. Intelligence, cyber operations, electronic warfare, missile defense, long-range strikes, civil defense, continuity of government functions, and nuclear consultation with the United States should be aligned through prearranged response options. 

Second, every base that hosts a major missile-defense system should be equipped with its own independent, low-cost counter-drone defense layer. This should include passive sensors, short-range radars, jammers, programmable airburst guns, low-cost missiles, decoys, protected power generation, and rapid recovery teams. 

Third, South Korea should also increase the depth of its interceptor magazine. Reload vehicles, storage and production facilities, and communications networks should be dispersed and protected. 

Fourth, the Kill Chain should concentrate less on searching for every mobile launcher and focus more on destroying the broader launch ecosystem, including tunnel entrances, command nodes, reloading points, transportation support, communications relays, and choke points. 

Fifth, Washington and Seoul also need a classified bilateral plan concerning North Korea’s limited nuclear use. This should regulate viable responses to a demonstrative nuclear explosion, an attack on military bases, and the use of nuclear weapons during a Taiwan contingency. 

Finally, South Korea should also prove that a single nuclear strike cannot paralyze the country. Thus, dispersed aircraft, alternative ports, hardened command posts, emergency runway repair, redundant communications hubs, and diverse measures for the continuity of government functions are at the core of a deterrence through resilience strategy. 

In all, North Korea’s nuclear threshold will rise only when Kim Jong-un concludes that limited nuclear options are not viable on the Korean Peninsula. Seoul should convince Pyongyang that a single nuclear attack would not fragment alliances, secure China’s protection, or end the war on North Korea’s terms, but would instead expose the North Korean regime to uncontrollable escalation and destruction. 

Dr. Ju Hyung Kim is President of the Security Management Institute, a defense think tank affiliated with the South Korean National Assembly. He researches East Asian security, military strategy, and alliance management and has published widely in international defense and foreign-policy outlets. Views expressed in this article are the author’s own. 

North Korea’s Emerging Limited Nuclear-Use Strategy was originally published on Global Security Review.

The simulated conflict ended without regime change in Pyongyang, allowing Kim Jong Un to claim a political victory. While avoiding nuclear escalation may seem prudent, such an outcome could deal a lasting blow to the credibility of America’s extended deterrence in East Asia.

The Guardian Tiger scenario should not be dismissed as an academic exercise. It reveals a critical vulnerability in the psychological foundation of deterrence: the perception among adversaries and allies of American willingness to use nuclear weapons in defense of its partners. If allies conclude that Washington will not cross the nuclear threshold even after a nuclear attack, they may question the value of the nuclear umbrella. Adversaries, meanwhile, may learn that nuclear coercion, carefully calibrated, can succeed.

In the simulation, North Korea escalated to a tactical nuclear strike against a South Korean Navy destroyer in the East Sea (Guardian Tiger I) and later against the Chinhae naval base (Guardian Tiger II), home to the Republic of Korea Navy’s Submarine Force Command and occasionally used for allied submarine visits. According to the report, American leaders debated nuclear retaliation but settled on conventional “pulsed” strikes.

In a real-world scenario, such strikes could plausibly involve precision-guided munitions from long-range bombers like the B1-B and Tomahawk cruise missiles launched from Arleigh Burke-class destroyers, aimed at targets such as missile transporter-erector launchers, hardened artillery positions along the DMZ, and command-and-control facilities near Pyongyang. In the exercise, the US stopped short of regime change, seeking to avoid further nuclear escalation and prevent a direct war with China—a decision that would have allowed Pyongyang to absorb the damage, count the survival of its regime as a strategic win, and enter negotiations from a stronger position.

Extended deterrence depends on more than military capability. It is rooted in the belief, shared by allies and adversaries alike, that the United States is willing to defend its partners by all means necessary, including nuclear weapons. An American failure to respond in kind to North Korean nuclear use would plant seeds of doubt. Japanese and South Korean leaders could begin to question whether Washington would truly “trade Los Angeles for Tokyo or Seoul” if the stakes involved limited nuclear use rather than an existential threat to the United States.

That doubt could trigger cascading effects. Calls in Seoul’s National Assembly for indigenous nuclear weapons, expanded production of the Hyunmoo‑4 ballistic missile, and pressure on Tokyo to more seriously pursue nuclear sharing arrangements have already entered the political debate.

This concern is amplified by North Korea’s 2022 nuclear weapons law, which openly authorizes preemptive nuclear strikes in scenarios ranging from an imminent attack on leadership to undefined overwhelming crisis situations. Analysts note that the law’s language effectively lowers the threshold for nuclear use, implying tactical employment to repel invasion and seize the initiative in war. Rather than viewing nuclear use as a desperate last resort, Pyongyang now appears willing to employ such weapons early. For example, a low‑yield detonation against South Korean or American forward-deployed forces to shock Washington and Seoul into political concessions.

The challenge grows sharper in the event of a dual contingency: simultaneous crises on the Korean Peninsula and in the Taiwan Strait. Guardian Tiger II simulated such a scenario, with China launching a multi-domain assault on Taiwan while North Korea escalated on the peninsula. In such a real-world situation, US Indo-Pacific Command could be forced to divert the USS Ronald Reagan Carrier Strike Group from Yokosuka to the waters east of Taiwan, deploy B‑52H bombers to deter Chinese operations, and even consider repositioning some Terminal High Altitude Area Defense and Patriot missile defense batteries from South Korea to protect American assets in Okinawa and Guam.

Such shifts illustrate how a stretched American posture could reduce missile interception capacity on the peninsula and temporarily remove some nuclear-capable platforms from immediate Korean defense. North Korea could calculate that Washington, already balancing a larger confrontation with China, would avoid nuclear escalation in Korea to conserve resources and limit the risk of an all-out US-China war.

The political and strategic consequences would ripple across the region. In Seoul, public and elite opinion could shift sharply toward developing an independent nuclear arsenal—something 71 percent of South Koreans already support. South Korea’s nuclear latency, widely assessed by proliferation experts, suggests it could potentially produce a weapon in as little as 6 months if political consensus formed.

In Tokyo, the debate over counterstrike capabilities, missile defense expansion, and potential nuclear sharing with the United States would intensify, potentially accelerating deployment of Tomahawk missiles and further integration of F‑35A fighters, which, in the US fleet, are being certified for B61‑12 nuclear bombs, into allied defense planning. Beijing, meanwhile, could seize the opportunity to position itself as a stabilizing broker, offering to mediate between Seoul and Pyongyang while shielding the latter from full international accountability, further eroding American influence.

Avoiding nuclear escalation in a limited-strike scenario is understandable, but Washington cannot afford such a decision to be interpreted as weakness. Strengthening deterrence credibility in Northeast Asia will require more than declaratory statements. Clear and credible red lines for nuclear use must be communicated both publicly and privately. Integrated nuclear-conventional planning with allies should ensure that flexible response options, from proportionate nuclear strikes to overwhelming conventional retaliation, are executable on short notice. Contingency planning must explicitly account for simultaneous conflicts in Korea and Taiwan, with pre-positioned munitions, dispersed basing arrangements for nuclear-capable aircraft, and rotational deployments of dual-capable ships and submarines to maintain strategic presence even under force diversion.

Equally important is sustained alliance signaling. These include high-visibility joint exercises like the US-ROK Freedom Shield exercises, regular port visits by nuclear-capable submarines, and trilateral missile tracking drills with Japan. These measures reassure allies, complicate adversary calculations, and demonstrate that any nuclear use will incur unacceptable costs.

The Guardian Tiger exercises are valuable not because they predict the future, but because they reveal how quickly deterrence can fray in the fog of crisis. A single decision to refrain from nuclear retaliation, however understandable at the time, could reverberate for decades and reshape the strategic balance in East Asia. In the nuclear age, preserving deterrence means guarding against both uncontrolled escalation and the perceptions of hesitation that could invite it.

Dr. Ju Hyung Kim, President of the Security Management Institute, a defense think tank affiliated with the South Korean National Assembly, is currently adapting his doctoral dissertation, “Japan’s Security Contribution to South Korea, 1950 to 2023,” into a book.

A Nuclear Umbrella in Peril: Lessons from North Korea’s Escalation Scenarios was originally published on Global Security Review.