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.

Japan and the Republic of Korea (ROK), as key American allies, should strengthen their conventional military capabilities, both offensive and defensive, to reinforce regional deterrence. Two critical steps are needed. First, Japan and South Korea must expand their capabilities to neutralize North Korea’s missile launchers. Second, Japan’s defense architecture should be aligned with South Korea’s Three-Axis System to create an integrated deterrence framework.

So far, to address concerns over potential nuclear decoupling, the US, Japan, and South Korea have explored multiple options. In addition to Washington’s repeated assurances that its nuclear extended deterrence remains intact, discussions have included modernizing American nuclear weapons, expanding nuclear-sharing agreements, redeploying tactical nuclear weapons to South Korea, and even the possibility of South Korea developing its own nuclear arsenal.

However, South Korea acquiring nuclear weapons remains highly improbable due to its significant political costs. From the 1960s to the 1980s, North Atlantic Treaty Organization (NATO) member-states feared the US might hesitate to retaliate with nuclear weapons if the Soviet Union launched a nuclear strike on Europe. While NATO pursued multiple strategies—most notably the dual-key system and the deployment of Pershing II missiles—these measures never fully resolved nuclear decoupling concerns.

Ultimately, NATO never confronted the full extent of this dilemma as the Soviet Union collapsed in 1991. Since the issue lies not in the US’s ability to retaliate but in its willingness to do so under specific conditions, the most practical approach is to adopt deterrence measures that North Korea perceives as credible.

First, Japan and South Korea should prioritize expanding their capabilities to neutralize North Korea’s nuclear missile launchers. A key advantage for the US, Japan, and South Korea—compared to NATO during the Cold War—is that North Korea is estimated to have around 50 nuclear warheads, far fewer than the tens of thousands in the Soviet arsenal.

In this context, Japan’s planned acquisition of enemy base strike capabilities should focus not only on expanding the number of available strike assets but also on improving their precision and destructive power to ensure maximum effectiveness against North Korean launch sites. At the same time, South Korea’s kill chain should further enhance its deep-strike capabilities by increasing assets like the Hyunmoo-4 missile, which is designed to penetrate deeply buried facilities.

Additionally, South Korea’s Drone Operations Command, established in 2023, should undergo a major expansion in drone assets capable of effectively detecting, tracking, and striking North Korean missile launchers. By integrating high-precision missiles and unmanned systems, both Japan and South Korea can significantly reduce North Korea’s ability to deliver nuclear strikes, thereby reinforcing deterrence.

Second, as Japan and South Korea expand their strike capabilities, Japan’s defense architecture should be aligned with South Korea’s Three-Axis System. This integration would allow both countries to allocate their finite military assets more effectively when targeting North Korea’s nuclear-related ground units. For example, given the geographic distance, Japan could focus on striking fixed targets such as command centers and underground missile storage sites while South Korea concentrates on eliminating mobile launchers that require rapid response and precision strikes.

Additionally, harmonizing Japan and South Korea’s missile defense structures would improve the likelihood of intercepting North Korean missiles. While Japan has developed its missile defense in close coordination with the United States, South Korea has opted to develop its own independent missile defense system, instead of fully integrating into the American-led ballistic missile defense framework.

However, aligning the two countries’ missile defense systems would significantly enhance regional interception capabilities. A fully integrated defense network would not only establish a more layered interception system against incoming North Korean missiles but also enable earlier response times—as Japan and South Korea deepen their real-time missile-tracking cooperation—South Korea’s response times could improve further. By improving both offensive and defensive coordination, Japan and South Korea can maximize deterrence and reduce North Korea’s nuclear strike effectiveness.

By implementing these measures, North Korea would be left with only a limited number of launchers capable of delivering nuclear weapons. While it is possible that some missiles could still be launched from the remaining launchers and a few might evade American missile defenses, North Korea would have to consider allocating few nuclear warheads against Japan, South Korea, and the United States. This would be necessary both to achieve its long-term political objectives and to deter US-ROK combined forces and US Forces Japan (USFJ) from retaliating in the short term.

Moreover, North Korean leadership would face significant uncertainty about whether its remaining nuclear missiles could successfully penetrate American missile defenses. In essence, by increasing their conventional strike capabilities and aligning their military strategies, Japan and South Korea could ensure that a substantial number of North Korean launchers are neutralized. This would force Pyongyang to operate with significantly reduced military options, making its attempt to create nuclear decoupling less credible.

However, this strategy is only viable as long as North Korea’s nuclear arsenal remains limited. If Pyongyang dramatically expands its warhead stockpile and launch platforms, conventional deterrence alone will no longer be sufficient, and the risk of nuclear decoupling will escalate beyond control. The US, Japan, and South Korea must act decisively—before the balance of power shifts irreversibly in North Korea’s favor. Time is running out.

Dr. Ju Hyung Kim, CEO 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.

Strengthening Nuclear Deterrence in the Far East was originally published on Global Security Review.