I. Major Variables to Assess Future Military and Security Environments Toward 2050

 

This paper examines the changes in the military and security environment surrounding South Korea and Japan at the regional (Northeast Asia, East Asia) and global levels. It also explores the directions and possibilities of security cooperation between South Korea and Japan. Addressing changes in the military-security environment over the next 25 years is a complex topic. Thus, this discussion will be guided by overarching logical structures rather than a precise temporal framework to accommodate the mid-to-long-term perspective. The future military-security environment involves various factors of change, but this paper will focus on the following key aspects:

 

First, changes in the global strategy of the United States and its security strategy in East Asia. As evidenced by the 2024 U.S. presidential election, the United States’ grand strategy in foreign and security affairs is undergoing fundamental transformation. These changes go beyond shifts between Republican and Democratic administrations or the emergence of unconventional leaders such as former President Donald Trump. The unipolar hegemonic systern that has persisted over the past 30 years has caused numerous issues, and the American public perceives the burdens of maintaining hegemony as increasingly unsustainable. The recent presidential election reflects the public’s evaluation and concerns regarding the country’s foreign and security direction. Consequently, the U.S. grand strategy in foreign and security affairs is expected to undergo significant changes. Notably, the weakening commitment to global engagement and East Asian involvement will substantially impact the security environment for South Korea and Japan. Given that both countries have maintained their security through strong military alliances with the United States, changes in U.S. military-security policies will be a major factor.

 

Second, the intensification of strategic competition between the United States and China. Strategic competition between the two nations initially emerged in the economic sphere but has evolved to encompass various aspects of national governance, including economic securitization, economic-security issues, politically influenced supply chain decoupling, the Biden administration’s de-risking policies, and broader decoupling policies under the Trump administration. Looking ahead, U.S.-China strategic competition is increasingly likely to shift into military rivalry and confrontations around key conflict areas in East Asia. This dynamic will significantly influence the military-security environment surrounding South Korea and Japan.

 

Third, changes in the nuclear environment in East Asia. Notably, China is rapidly modernizing its nuclear weapons and delivery systerns. Nuclear parity between the United States and China could be achieved within the next decade, potentially signaling the emergence of mutual assured destruction (MAD). Such developments in nuclear dynamics will have significant implications for U.S.-China gray-zone conflicts and broader military competition. Furthermore, the New START Treaty between the United States and Russia is expected to expire in February 2026. The potential collapse of strategic nuclear agreements, which have been a cornerstone of U.S.-Russia relations since the 1970s, could usher in a new era of nuclear competition among major powers. Given the ongoing war in Ukraine, further deterioration in U.S.-Russia relations is anticipated, intensifying nuclear competition as a grave threat. Additionally, North Korea’s advanced nuclear and missile capabilities will remain a significant variable. Though North Korea has long posed a continuous threat to the security of South Korea and Japan, its strengthening strategic cooperation with China and Russia is likely to further impact security cooperation involving South Korea and Japan.

 

Fourth, advancements in cutting-edge technology will profoundly affect the military-security environment. The rapid development of automation and autonomy technologies is driving transformative changes in military technology. Emerging technologies, such as generative AI, anticipated general and superintelligence, quantum computing, quantum encryption, and quantum communication, will have substantial applications in the military domain. As these technological changes accelerate within the next decade, understanding their impact on the security environment of South Korea and Japan will be crucial.

 

Fifth, non-traditional military-security issues, such as environmental challenges, ecological crises, and health emergencies, will increasingly influence matters within the realm of the military and security. These critical issues, potentially escalating to existential threats, could intensify interstate conflicts and may necessitate military measures for resolution. The COVID-19 pandemic demonstrated the strengthening of state jurisdiction and regulatory power to manage crises. Looking ahead, ecological crises driven by climate change are expected to worsen. In this context, states may resort to military conflict to protect their populations, making this an area of significant concern.

 

II. Changes of the U.S. Strategy and the Future of U.S.-China Rivalry

 

The 2024 U.S. presidential election signals long-term changes in America’s security strategy. Since World War II, the United States has pursued a foreign and security strategy aimed at establishing and maintaining a liberal international order. While ostensibly promoting collective security, this strategy has in practice involved providing security as a public good based on alliances.

 

This hegemonic strategy has allowed U.S. foreign policy to encompass a broad spectrum, combining elements of neo-isolationism, restraint, and balancing, particularly evident in the Republican Party’s grand strategy. However, after three decades of experiencing a unipolar hegemonic systern, the U.S. is now adopting a security strategy increasingly focused on its national interests.

 

A more fundamental concern, as revealed in the last presidential election, is that former President Trump not only opposes the liberal grand strategy but also appears averse to U.S. global leadership itself. Should the U.S. abdicate its global leadership role or its hegemonic position in international politics, significant changes to the international order would ensue. If the U.S. prioritizes its own interests while disregarding the existing multilateral, rules-based order, the world could undergo its most fundamental transformation since World War II.

 

Trump’s foreign and security strategy is likely to pose significant challenges to U.S. allies, including South Korea and Japan. Traditionally, the U.S. hegemonic strategy has been characterized by a benevolent approach, providing security as a public good in exchange for economic concessions from its allies. However, the Trump administration’s simultaneous demands for economic concessions, increased defense cost-sharing, and greater military contributions may be perceived as a coercive hegemonic strategy. This shift may erode trust between the U.S. and its allies, creating opportunities for China to exploit divisions within the U.S. alliance systern. Indeed, China appears to expect that Trump’s pressure will accelerate independent foreign and security strategies among U.S. allies, weakening the overall alliance framework.

 

President Trump is expected to strongly demand increased defense cost-sharing from allies while also seeking greater military contributions to bolster global deterrence, particularly against China. These demands deviate from traditional U.S. hegemonic strategy and are likely to generate confusion and resistance among allies.

 

South Korea and Japan are particularly sensitive to Trump’s foreign policy approach. Both countries rank among the top nations with trade surpluses with the U.S. and are perceived by Trump as not contributing enough to defense costs. Additionally, both nations host some of the largest U.S. overseas military bases and a substantial number of U.S. troops.

 

Along with Trump, key Republican figures have also publicly argued that U.S. military support should now be leveraged not only against North Korea but also to contain China. South Korea and Japan must carefully evaluate their responses to Trump’s demands for increased defense contributions while also determining their roles in U.S. efforts to counter China. This includes addressing the potential changes in the role of U.S. forces in the event of a contingency involving Taiwan and preparing strategies to North Korea’s continued provocations. These challenges necessitate a diplomatic approach that balances security and economic interests for both nations.

 

III. Emerging Technology and Uncertain Future of Security Environments

 

The recent wars in Ukraine and Gaza demonstrate that AI is already being utilized across multiple dimensions of warfare, a trend that is expected to accelerate and persist in the medium to long term. As nuclear weapons, conventional arms, and psychological and information warfare converge with AI, these domains will rapidly evolve into AI-based nuclear weapons, autonomous weapon systerns, and cognitive warfare. South Korea and Japan are also expected to face changes in the military-security environment driven by advanced technologies in the future. As democratic nations, they have strived to establish common norms, but going forward, there is a need for more pragmatic responses in addressing military and security challenges.

 

AI, as a general-purpose technology, functions as a meta-enhancement that strengthens existing technologies. It not only improves specific weapon systerns but also transforms the operational frameworks of warfare, decision-making processes related to conflicts, and the perceptions and responses of governments, military institutions, and societies. AI’s multidimensional nature ensures its pervasive influence on the future of conflict.

 

Given the geopolitical competition among nations, the likelihood of preventing the military utilization of AI technology is slim. Moreover, there is a possibility that AI could rapidly develop in unintended directions, potentially escaping human control. Nations widely recognize AI as an innovative tool for bolstering national security, making it unlikely that proactive caution regarding military AI technologies will emerge until an event demonstrates the shared harm AI poses to the international community. It is imperative to comprehensively assess the current applications of AI in nuclear weapons, autonomous weapon systerns, and cognitive warfare. Equally critical is anticipating the common challenges these advancements might present and initiating serious discussions to address them in a timely manner.

 

The integration of AI into nuclear systerns significantly increases the risk of unintended nuclear conflicts. First, AI-driven decision-making can lead to miscalculations based on flawed data or misinterpretations of adversary actions, potentially escalating tensions. The accelerated decision-making enabled by AI leaves less time for human deliberation, increasing the likelihood of errors and misjudgments. Second, AI systerns are highly vulnerable to cyberattacks, such as data manipulation, hacking, or “data poisoning,” which could distort nuclear command systerns, trigger false alarms, or hinder appropriate responses. The interconnected nature of networked systerns also amplifies the risk, as a single malfunction can cascade through the entire systern. Third, over-reliance on AI or distrust in its judgments may undermine human control in critical moments, delaying or misguiding decisions on nuclear weapon use. The opacity of AI’s decision-making processes, known as the “black-box” problem, further complicates oversight and correction. Lastly, AI integration threatens strategic stability by enhancing surveillance and reconnaissance capabilities, potentially enabling preemptive strikes and increasing “use-it-or-lose-it” pressures on nuclear arsenals. Moreover, the adoption of AI fosters a technological arms race, exacerbating global military competition and instability.

 

Second, the rapid development of autonomous weapon systerns (AWS) integrated with AI has escalated global military competition, raising significant ethical, legal, and strategic concerns. AI-driven AWS, such as autonomous drones and swarm technologies, pose challenges due to their unpredictable behavior in dynamic environments, accelerated decision-making that heightens the risk of unintended conflict escalation, and the ease of mass production, making these systerns accessible to non-state actors and terrorists. Moreover, their potential use for targeted killings, including ethnic cleansing, amplifies risks of bias and disproportionate harm, as evidenced by flaws in facial recognition technologies. Despite international calls for regulation, major powers like the U.S., China, and Australia are advancing military AI projects, further fueling the arms race.

 

In the long term, AWS development is expected to significantly alter warfare dynamics, enabling faster, automated combat while minimizing human involvement. However, the potential for systern errors and malfunctions increases the likelihood of heightened tensions between nations. In the context of U.S.-China strategic rivalry, both nations are aggressively pursuing military AI advancements to secure dominance, risking strategic stability. This competition not only threatens global military balance but also introduces complex ethical and legal dilemmas that demand international cooperation to address the far-reaching consequences of autonomous weapon systerns.

 

Third, cognitive warfare, conducted at the international level by adversarial forces, represents a form of cyber conflict where organized groups manipulate online discourse and discredit political opponents through misinformation, propaganda, and manipulative techniques. This includes tactics such as spreading unfounded claims to destroy reputations and using profile-based micro-targeting to weaken political institutions, potentially leading to widespread insurgency and the collapse of existing political orders. AI significantly enhances the sophistication and effectiveness of cognitive warfare strategies by enabling precise psychological manipulation, dissemination of false information, and influencing beliefs and behaviors. Emerging technologies like AI and neurotechnology act as key enablers of cognitive warfare, driving nations to militarize dual-use technologies and accelerate technological arms races. This competitive dynamic often undermines ethical, legal, and normative constraints, as states prioritize disruptive capabilities to maintain national security. As a result, cognitive warfare normalizes the militarization of the mind, fosters irresponsible actions in the cognitive domain, and hinders the establishment of norms protecting mental privacy, autonomy, and integrity. Furthermore, these dynamics exacerbate technological decoupling among major powers, intensifying global tensions (Chun 2024).

 

IV. Shifting Nuclear Balance among East Asian Countries

 

1. China’s Nuclear Modernization

 

According to DoD annual report on Military and Security Developments Involving the People’s Republic of China, China’s longstanding national strategy is to achieve “the great rejuvenation of the Chinese nation” by 2049 (Office of the Secretary of Defense 2022). This strategy determinedly pursues political, social, economic, technological, and military development to increase the PRC’s national power and revise the international order in support of the PRC’s systern of governance and national interests. The PLA has sought to modernize its capabilities and improve its proficiencies across all warfare domains to become a joint force capable of the full range of land, air, and maritime as well as nuclear, space, counterspace, electronic warfare, and cyberspace operations.

 

In the first stage from 2021 to 2035, the CCP aims for the PRC to “basically” meet its initial thresholds for becoming a “great modern socialist country.” In this stage, the PRC will likely continue to prioritize economic development as “the central task” but, rather than rapid economic growth, it will seek to address its uneven economic development and inequalities that Beijing recognized as the new “principal contradiction” in PRC society in the “New Era.” By 2035, the PRC seeks to increase self-reliance through enhancing its economic and technological strength, including “basically” completing its military modernization by becoming a “global leader in innovation” and enhancing self-sufficiency in key areas like food supply. The PRC intends to significantly strengthen its cultural “soft power” and improve its domestic rule of law and governance systerns.

 

In the second stage from 2035 to 2049, the PRC aims to attain national rejuvenation and Chinese modernization, realizing an international status that Xi describes as a “global leader in terms of comprehensive national strength and international influence.” A renewed PRC will have attained—among the CCP’s many goals—its objectives to field a world-class military and assume a leading position in an international order revised in line with the PRC’s overall foreign policy goal to establish what it refers to as a “community of common destiny” or, the PRC’s preferred official English translation, “community with a shared future for mankind.”

 

Over the next decade, China is expected to rapidly modernize, diversify, and expand its nuclear forces to provide options across the escalation ladder, from low-yield precision strike missiles to high-yield ICBMs. The Department of Defense (DoD) estimates that China’s nuclear stockpile surpassed 600 operational warheads in 2024 and is projected to exceed 1,000 by 2030, with further expansion planned through 2035 to achieve the PLA’s modernization goals. Beijing’s use of fast breeder reactors and reprocessing facilities, ostensibly for peaceful purposes, likely contributes to its nuclear weapons program. Additionally, China is arming its solid-propellant silo fields, which include 320 silos across three new fields, and expanding its DF-5 liquid-silo force to approximately 50 silos. These efforts align with Beijing’s strategy to establish an “early warning counterstrike” posture, enhancing the survivability and responsiveness of its launch sites (Kristensen et al. 2024, 49–72).

 

 

Projections for the growth of China’s nuclear weapons stockpile depend significantly on assumptions about how China’s three new solid-fuel missile silo fields will be armed.

 

 

Source: (Kristensen et al. 2024).

 

China’s growing nuclear capabilities enable the PLA to target more U.S. cities, military facilities, and leadership sites, marking a shift from a minimal deterrence strategy focused on MAD to one capable of inflicting greater damage in a nuclear exchange. This modernization includes the development of advanced delivery systerns to counter U.S. missile defenses and lower-yield weapons for more discriminate strikes, suggesting that Beijing aims to sustain multiple rounds of counterstrikes and increase its ability to dominate in a nuclear conflict. These advancements highlight China’s long-term commitment to achieving a “world-class” military by 2049.

 

China’s nuclear strategy emphasizes deterrence against a first strike and counterstrike capabilities to retaliate against an adversary’s military, population, and economy, aiming to de-escalate conflicts and return to conventional warfare while maintaining sufficient force to deter further aggression. Although Beijing upholds a no-first-use (NFU) policy, ambiguities exist, as the PRC may consider nuclear first use in response to non-nuclear threats endangering its nuclear forces, command and control (C2), or the survival of the CCP regime, particularly in scenarios involving Taiwan. The combination of conventional and nuclear missile forces and the dispersal of mobile systerns during conflicts complicate the identification of missile types and escalation management, increasing the risk of inadvertent attacks on nuclear assets and “use-or-lose” pressures. This strategic ambiguity remains a key challenge for adversaries attempting to navigate deterrence and escalation dynamics with the PRC (Kristensen et al. 2024, 101–102).

 

China’s nuclear forces, when developed to achieve parity or near parity with the United States, could enable China to adopt a more assertive gray zone strategy. To date, China has adhered to a minimum deterrence strategy aimed at countering potential U.S. aggression. However, as U.S.-China military competition accelerates and China’s gray zone strategies become increasingly aggressive, its nuclear forces are expected to play a more significant role. In a scenario of military conflict between China and the U.S. and Taiwan over Taiwan, China may utilize its nuclear strategies in various ways.

 

Currently, China’s comparatively weaker nuclear forces make it wary of escalation in gray zone disputes, fearing they may lead to full-scale conventional warfare and potentially nuclear conflict with the U.S., where China’s nuclear capabilities remain inadequate. However, in a decade or more, when nuclear parity or mutual assured destruction is achieved, China may feel less compelled to exercise restraint in gray zone strategies.

 

China has already demonstrated the use of complex strategies in gray zone conflicts, and if nuclear capabilities are incorporated, it is likely to adopt even more assertive approaches. This could lead to an expansion of China’s aggression in areas such as the South China Sea, East China Sea, and Taiwan, posing significant security threats to South Korea and Japan.

 

2. Multipolar Nuclear Strategic Environment in Northeast Asia

 

The challenges to strategic stability in a multipolar world are becoming increasingly evident as the erosion of US-Russia arms control frameworks, exemplified by the suspension of New START, highlights the fragile nature of bilateral agreements. The shift toward a multipolar nuclear order, with China’s growing arsenal and its potential role in a broader arms race, complicates efforts to maintain stability. Meanwhile, Russia’s actions in Ukraine, including its misuse of nuclear deterrence, expose the limitations of existing arms control and nonproliferation agreements in addressing modern geopolitical crises. These developments raise concerns about the adaptability of traditional strategic stability concepts to a multipolar environment, where technological advancements and the integration of emerging nuclear powers demand new approaches (Kühn 2023).

 

As the post-Cold War order concludes, great power geopolitical competition intensifies, with the emergence of what could be termed “the axis of revisionism.” This includes the ongoing Ukraine war, closer strategic ties between China and Russia, the military alliance between North Korea and Russia formalized in June 2024, and Iran’s military support to Russia’s Ukraine war through drone supplies. Well-documented missile cooperation between North Korea and Iran further adds to these dynamics. Together, military cooperation among North Korea, China, and Russia is likely to have profound implications for Northeast Asian geopolitics.

 

While the bilateral nuclear balance between the U.S. and Russia has been pivotal, the emerging era will prioritize a multipolar nuclear order. Strategic agreements between the U.S. and Russia may not be extended, and the likelihood of nuclear arms negotiations between the U.S. and China remains extremely low. Meanwhile, North Korea continues to enhance its nuclear and missile capabilities despite international sanctions. The strategic cooperation among North Korea, Russia, and China is accelerating in this context (Eom 2024).

 

Although a formal trilateral alliance has not yet emerged, strategic contradictions and overlaps exist among these nations’ interests. Nonetheless, their common opposition to the U.S. could drive closer collaboration, particularly if the U.S.’s relative military strength declines. If Russia utilizes nuclear power to alter the status quo in Europe, China and North Korea may similarly combine their nuclear capabilities to seek changes in Northeast Asia. Such developments would compel the U.S., South Korea, and Japan to address a multifaceted nuclear threat.

 

In such a scenario, challenges arise over how the U.S. could extend nuclear deterrence to South Korea and Japan, and how the region could collectively respond to a hybrid nuclear threat posed by North Korea. Conversely, international and multilateral cooperation to address these developments remains limited.

 

V. Prospects for South Korea-Japan Security Cooperation Toward 2050

 

Long-term security cooperation between South Korea and Japan becomes increasingly critical. First, if the U.S. East Asia security strategy undergoes fundamental shifts, both nations could face heightened security threats. Since World War II, South Korea and Japan have relied on close alliances with the U.S. to ensure their security. During the Cold War, their strategy was centered on countering the military threats from communist forces, with the U.S. alliance serving as the axis of this framework. As Victor Cha has noted, when U.S. security commitments to East Asia weaken, South Korea and Japan have historically accelerated security cooperation despite bilateral tensions (Cha 1999). While this trend has not always been consistent, a weakening U.S. security commitment underscores the growing necessity for South Korea-Japan security collaboration. If U.S. foreign policy shifts further toward Trumpian “America First” doctrines or offshore balancing strategies, the security needs of South Korea and Japan will inevitably increase. Managing bilateral issues effectively while establishing new frameworks for security cooperation will be crucial.

 

Second, as U.S.-China strategic competition intensifies, South Korea and Japan will face similar security challenges. The U.S. may leverage the South Korea-U.S. and U.S.-Japan alliances to counter China’s security threats, requiring both countries to increase defense spending and adapt their strategic frameworks. This burden is heavier for South Korea. Japan already maintains direct military tensions with China, particularly in the East China Sea, and has been proactively pursuing changes in the U.S.-Japan alliance to counter China’s military rise. In contrast, South Korea has yet to formulate clear strategic responses, despite the Taiwan Strait crisis posing a significant threat to its supply chains and economic security.

 

In the long term, if China secures dominance in the first island chain and integrates regions within the Belt and Road Initiative into its security sphere, South Korea and Japan will face shared exposure to China’s threats. As U.S.-China competition escalates into military confrontation, and as Taiwan Strait and South China Sea issues impact the protection of supply routes, economic security, and military security in South Korea and Japan, the need for cooperation will only intensify.

 

South Korea and Japan also face the challenge of balancing their deep economic ties with China while addressing U.S. demands for military containment of Beijing. The broad areas of cooperation under frameworks such as China-South Korea-Japan trilateral initiatives further complicate strategic responses to U.S.-China competition for both countries.

 

Third, amid the rapid advancement of cutting-edge technology, South Korea-Japan technological cooperation is increasingly vital. On the one hand, both countries must prevent the military exploitation of advanced technologies that could destabilize strategic stability in East Asia. As liberal democracies, they should collaborate to establish international norms to prevent the militarization of AI and other emerging technologies.

 

At the same time, they must prepare for great power geopolitical competition leveraging advanced technologies. China’s potential to surpass the U.S. in military AI and quantum technology could rapidly shift the military balance. Despite changes in the U.S. global strategy, technological cooperation among the U.S., South Korea, and Japan remains indispensable. Even with lukewarm U.S. engagement, sustained South Korea-Japan cooperation in advanced technology is crucial. This necessitates close dialogues to evaluate security environments and align security strategies between the two nations.

 

Fourth, the issue of the future global nuclear order is directly linked to the security interests of South Korea and Japan. If the U.S. extended deterrence commitment weakens while nuclear capabilities of China, North Korea, and Russia grow, coupled with strengthened cooperation among these states, it would pose a critical threat to the security of both South Korea and Japan. Therefore, it is important to identify areas where South Korea and Japan can cooperate to address challenges.

 

First, South Korea and Japan need a shared understanding of the weakening and possible collapse of the global nuclear order. As non-nuclear weapon states surrounded by nuclear-armed nations, South Korea and Japan share a common predicament. Thus, they should strongly advocate for the strict adherence to the Nuclear Non-Proliferation Treaty (NPT), the suppression of vertical nuclear proliferation among major powers, and the necessity of arms control negotiations among nuclear-armed states. In this process, efforts should also be made to establish a multilateral framework that addresses the complete denuclearization of North Korea. Additionally, it is crucial to recognize that the nuclear order in Northeast Asia carries significant global implications and to devise joint measures to address this issue on a global scale.

 

Second, though immediate prospects for nuclear arms control agreements between the U.S. and China are limited, the importance of dialogue and laying the groundwork for future negotiations must be underscored. South Korea and Japan, as key U.S. allies, should actively support U.S.-led efforts to initiate crisis management discussions with China, emphasizing the need for transparency and responsible nuclear strategy. Both nations must strengthen regional coordination with the U.S. to ensure unified messaging while enhancing their own deterrence capabilities, particularly in missile defense, to complement U.S. efforts and maintain regional stability. Furthermore, they should advocate for China’s inclusion in multilateral arms control frameworks, such as through the P5 or regional security mechanisms, encouraging broader engagement and accountability. By aligning closely with U.S. strategies and promoting multilateral dialogue, South Korea and Japan can contribute to reducing risks and ensuring stability amidst increasing U.S.-China strategic competition (Santoro 2023).

 

Third, given the growing nuclear threats, joint efforts between South Korea and Japan are necessary to strengthen the U.S. extended deterrence commitment. Although South Korea and Japan maintain bilateral alliances with the United States, they face common challenges due to nuclear threats from neighboring countries. The Camp David Agreement includes provisions for immediate consultations in the event of issues significantly affecting regional security. Similarly, close cooperation among South Korea, Japan, and the United States is essential when nuclear threats from neighboring countries escalate. The core of this effort lies in the U.S. extended deterrence commitment, and it will require a shared understanding between South Korea and Japan as well as coordinated demands on the United States to continuously enhance this commitment.

 

Fourth, if North Korea’s nuclear threat intensifies and the U.S. extended deterrence weakens, South Korea may feel an increasing necessity for independent nuclear armament. In such a scenario, South Korea would inevitably face concerns about economic sanctions from the United States and the international community, as well as fears of a nuclear domino effect involving Japan and potentially Taiwan. If South Korea finds no alternative to independent nuclear armament, it will need to work closely with Japan in advance to establish mechanisms to convince Japan that South Korea’s nuclear armament contributes to Japanese security and regional nuclear deterrence in Northeast Asia. Exploring the feasibility of prior consultations or dialogues between South Korea and Japan will be crucial to prevent South Korea’s nuclear armament from undermining the global nuclear order.

 

Lastly, both South Korea and Japan need a common preparation for the scenario where nuclear parity is achieved between China and the United States, accompanied by mutual assured destruction. As aforementioned, if China attains nuclear parity with the United States, it is likely to adopt more aggressive gray zone strategies in conflict zones across East Asia. This would pose shared threats to South Korea and Japan, necessitating the sharing of threat perceptions and coordinated responses. Both countries should demand greater transparency from China and effectively convey their shared intent to both the United States and China to encourage nuclear arms control negotiations between the two powers.

 

Despite existing differences and perception gaps between South Korea and Japan on various issues and within security contexts, they will ultimately face common military threats and the necessity for long-term cooperation. Thus, sustaining multidimensional consultative efforts from now is vital to fostering long-term cooperation.

 

References

 

References

 

Ahn, Kyungmo. 2024. “The New Cold War and the North Korea-China-Russia Triangle: Strategic Implications.” Global North Korea (EAI) Special Report, December 20.

 

Cha, Victor D. 1999. Alignment Despite Antagonism: The United States-Korea-Japan Security Triangle. Stanford, CA: Stanford University Press.

 

Chun, Chaesung. 2024. “Military Challenge ②: The Development of AI-Based Autonomous Weapon systerns, Cognitive Warfare, and Changes in the Military Security Order.” EAI National Security Research Center Special Report, September 6.

 

Eom, Gu Ho. 2024. “The DPRK-Russia-China Triangle Under Trump 2.0: Future Prospects and Strategic Responses.” Global North Korea (EAI) Special Report, December 13.

 

Jun, Jaewoo. 2024. “China’s Calculus on DPRK-Russia Alignment: A Geopolitical Perspective.” Global North Korea (EAI) Special Report, December 13.

 

Kristensen, Hans. 2024. “The 2024 DOD China Military Power Report.” Federation of American Scientists, December 18.

 

Kristensen, Hans M., Matt Korda, Eliana Johns, and Mackenzie Knight. 2024. “Chinese Nuclear Weapons, 2024.” Bulletin of the Atomic Scientists 80, 1: 49–72, 101–102.

 

Kühn, Ulrich. 2023. “Strategic Stability in the 21st Century: An Introduction.” Journal for Peace and Nuclear Disarmament 6, 1: 1–8.

 

Office of the Secretary of Defense. 2022. Military and Security Developments Involving the People’s Republic of China: Annual Report to Congress Pursuant to the National Defense Authorization Act for Fiscal Year 2000. Washington, DC: Department of Defense.

 

Santoro, David. 2023. “Getting Past No: Developing a Nuclear Arms Control Relationship with China.” Journal for Peace and Nuclear Disarmament 6, 1: 68–86.

 

 

 

■ Chaesung Chun is Chair of EAI’s National Security Research Center and Professor at Seoul National University.

 

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■ Translated and edited by Chaerin Kim, Research Assistant
    For inquiries: 02 2277 1683 (ext. 208) | crkim@eai.or.kr