In an era of overlapping crises, South Korea’s security environment is no longer defined by either a single enemy or a theater. Instead, it is shaped by simultaneity. The probability of a dual contingency—China’s attempt to occupy Taiwan by force combined with North Korea’s opportunistic behavior on the Korean Peninsula—is no longer a far-fetched scenario. Meanwhile, the growing concern that Moscow could directly test NATO’s resolve before 2030 has reemerged as the possibility of a large-scale conflict in Europe. The result is a structural change. South Korea’s indispensable ally, the United States, could face challenges that have to manage multiple high-intensity crises at the same time.
For decades, South Korea’s defense posture was rooted in the following assumption: that in the case of a Korean contingency, US troops would be swiftly and massively reinforced, backed by Japan’s role as a rear-area supporter—in accordance with OPLAN 5055, which outlines a US-Japan joint response in a Korean contingency. However, the assumption is now under pressure. In a dual contingency scenario that includes both Taiwan and the Korean Peninsula, US troops in East Asia could be bogged down, while reinforcement from the continental United States could be either delayed or diverted. If Russia escalates tensions in Europe, US military assets would be further thinned out.
To be sure, this does not mean that the US alliance is weakening; it remains as the bedrock of South Korea’s security. Nonetheless, the guarantee that the alliance with the US alone would be sufficient no longer applies under systemic strain. The implication is clear. South Korea should strengthen deterrence, enhance resilience, and build additional security layers with like-minded countries that could mitigate the risk of US overstretch.
Among the potential partners, two countries—Japan and Canada—particularly stand out.
Japan is pivotal for reasons that are as much geographical as they are strategic. Any major crisis in the Korean Peninsula or in the Taiwan Strait would inevitably involve Japanese territory, bases, and their related facilities. Needless to say, U.S. Forces Japan (USFJ) would serve as a critical hub for logistics, air and naval operations, missile defense, and US reinforcement. The sea lines of communication (SLOCs) that link the Korean Peninsula to the broader Indo-Pacific run through Japan’s adjacent waters. Practically speaking, a Korean contingency that does not involve Japan is unthinkable—albeit the extent of Japan’s potential engagement remains contestable.
Despite such a reality, Japan-South Korea security cooperation has long been constrained by historical disputes and political sensitivities. This constraint is real and cannot be ignored. Nevertheless, the strategic environment is shifting way faster than the political narratives that have framed the bilateral relationship for decades. North Korea’s advancing missile and nuclear capabilities, China’s growing military assertiveness, and the growing likelihood of the Taiwan contingency have fundamentally altered the cost-benefit calculus of non-cooperation in the security domain.
The logic is not ideological; it is operational. Missile alarm systems, maritime surveillance, and air defense are the areas where both Japan and South Korea possess complementary capabilities. In a crisis scenario, real-time intelligence sharing, coordinated responses, and deconflict operations could not only determine the effectiveness of deterrence but also the outcome of the early stages of the war. Although the trilateral cooperation with the United States—most notably the 2023 Camp David trilateral summit—has partially addressed these problems, the bilateral coordination between Tokyo and Seoul remains underdeveloped relative to the scale of the challenge at hand. Creative measures like integrating Japan’s enemy base strike capability with South Korea’s Three-Axis System could enhance collective deterrence in a meaningful way.
If Japan is essential due to its geographical proximity, Canada is invaluable because of connectivity. At first glance, Canada’s geographical distance illustrates a limited role when it comes to the Korean Peninsula. Nonetheless, such an understanding is misleading. Canada is one of the few countries that operate both within the Indo-Pacific and the Europe-Atlantic strategic spaces. As a member of the G7 and NATO—and a country with a growing Indo-Pacific strategy—Canada occupies a unique position as a bridge between increasingly interconnected regions.
For South Korea, such a bridging function is extremely invaluable strategically. The emerging alignment among Russia, China, and North Korea is not confined to a single theater; it extends across Eurasia, linking the security dynamics of Europe and the Indo-Pacific. In such an environment, South Korea’s partnerships should overcome regional boundaries. Canada offers the strategic scope.
Furthermore, Canada provides contributions that go beyond conventional military power. The implementation of sanctions against North Korea, epitomized by Operation NEON, maritime domain awareness (MDA) operations, and its contribution to monitoring illicit ship-to-ship transfers, showcases that Canada is already making a contribution in maintaining stability on the Korean Peninsula. At the same time, strengths in the fields of key minerals, energy, advanced technology, and defense industrial capacity elevate Canada as an important partner in building up economic and industrial resilience—on which modern deterrence is increasingly dependent.
Therefore, the strategic value of Japan and Canada lies in complementarity. While Japan serves as a pillar that buttresses South Korea’s immediate operational environment, Canada connects that environment to a democratic middle-power coalition that could sustain pressure across multiple domains. These two countries create the core of a secondary layer of security cooperation that could strengthen the US alliance without replacing it.
To translate the aforementioned strategic logic into practical policy, South Korea should pursue a set of specific measures.
First, Tokyo and Seoul should institutionalize a bilateral security coordination mechanism that goes beyond ad hoc political arrangements. Here, measures should include the establishment of a standing channel for real-time intelligence sharing, joint planning for missile defense and maritime operations, and coordinated contingency planning for evacuation and logistics. The mechanism should be designed to function under politically tense conditions, ensuring continuity during crises. Using the 1904 Entente Cordiale—where Britain and France probe ways to deepen bilateral relationships without signing a defense treaty—as a historical reference point would be a start.
Second, Japan and South Korea should develop a structured framework that would enable rear-area support in a Korean contingency. This includes pre-agreed arrangements on the use of ports, airfields, maintenance facilities, and supply chains. To be sure, the current OPLAN 5055 should contain these elements—the details of the plan are not open to the public, yet the US and the Japanese government are fully aware of the plan. Nonetheless, Japanese should discuss with their South Korean counterparts at least the core elements of the plan. By clarifying these roles, both countries could reduce uncertainty and reinforce the credibility of deterrence.
Third, Japan, Canada, and South Korea should introduce a middle-power trilateral dialogue that is centered on dual contingency scenarios. The dialogue should address supply chain resilience, sanctions coordination, cyber defense, and operational implications of a crisis that may occur in Europe and in the Indo-Pacific concurrently. Unlike the existing US-led framework, the platform should underscore the role of middle powers that stabilize the international order in an environment of great-power rivalry; the approach would be aligned with Prime Minister Carney’s key message at the recent Davos.
Fourth, Ottawa and Seoul should deepen defense industrial cooperation. Partnerships in joint munition production, naval platform construction, and emerging technology domains like artificial intelligence and autonomous systems would reinforce the two countries’ capability to sustain operations in a protracted crisis. If the Canadian Patrol Submarine Project (CPSP) favors the South Korean submarine this year, bilateral industrial cooperation would gain clear momentum in the years ahead. In an era where the availability of equipment and ammunition shapes the trajectory of conflict, such cooperation is no longer optional.
Fifth, Canada and South Korea should expand cooperation in MDA and sanctions implementation. By integrating surveillance capabilities, intelligence sharing, and coordinating patrol activities, both countries could effectively respond to North Korea’s attempts at sanctions evasion.
Last, but not least, South Korea should define partnerships with Japan and Canada as alliance multipliers, instead of alternatives to the United States. The key objective should be to enable alliances to function effectively even under extreme stress, rather than reducing dependence on Washington. By building additional layers of cooperation, South Korea could contribute to a more resilient and adaptable security framework.
The newly developing strategic environment requires a shift in mindset. Security can no longer be understood as a function of a mere bilateral alliance. It is increasingly shaped by a cooperative network that spans regions, domains, and levels of capability. For South Korea, Japan and Canada are far from simple secondary partners. They are central to the construction of a security framework that could withstand the pressure of an increasingly unstable world.
In this context, the question is not whether South Korea needs to deepen cooperation with Japan and Canada. Rather, it is whether it can afford not to.
