Regional Security Complexes – East Asia 2024-2025

Regional Security Complexes – East Asia 2024-2025

by Jelena Milovanović

Introduction 

East Asia is a region where historical development has led to a composite security structure. Deep economic links and rapid development are equally important to understanding this region as its long-standing rivalries and disputes. Historical grievances, proximity-based threats, and overlapping spheres of influence have created a tightly woven security environment that cannot be fully understood simply by a state-to-state analysis. The behaviour of state actors cannot be looked at in isolation but must be examined in the context of their proximity to other states, creating unique and ever-changing dynamics in regions. Regional Security Complex Theory (RCST), created by Buzan and Waever, provides a very useful lens for looking at and understanding regional security dynamics and interdependence. This analysis aims to take a closer look at the regional level in East Asia today and answer questions about current trends in the region and security dynamics, but also its interregional interactions with nearby regions and global actors. 

Applying RSCT to East Asia 

In the book Regions and Power, Buzan et al argue that the end of the Cold War signalled a restructuring of regional security complexes in East Asia1. They argue that the security complex of Northeast Asia and the security complex of Southeast Asia, which had previously been interregionally linked, created a single East Asian RSC. The first reason for that is that the ending of the Cold War allowed China to strengthen links with Southeast Asia that it had already formed. Without a strong influence of the Soviet Union in the region, China was able to position itself as a dominant actor. The second reason is the economic links between countries. The approach that East Asia took after the Cold War can be described as consisting of multilateralism and comprehensive security. Comprehensive security is an approach first adapted by Japan and originally called sōgō anzen hoshō in Japanese, and over time, it became a characteristic of the entire region. It is a holistic and integrated approach showing that the broadening of the concept of security has very much impacted the development of security in this region. Economic security, in particular, economic development and ties between countries, is one area that has been integral to East Asia.   

The principal actors include Japan, China, South Korea, North Korea, but also increasingly Southeast Asian countries like Vietnam and the Philippines. China’s consistent assertiveness and growth have impacted the entire region and become a key factor around which other countries in the region build their security policies and alignments. Buzan and Waever describe regions not as fixed entities, but as „process formations,“ and so is the case with East Asia. This region has, throughout time, changed from the Cold War era bipolar system into something with more layers and complexity.   

Recent Developments 

In April 2025, China conducted extensive military drills surrounding Taiwan, involving naval, air, and ground units, which it described as a “stern warning to separatist forces“. Taiwan, on the other hand, has tried to shift towards self-reliant capabilities (such as undersea defence), while also deepening its security cooperation with the Philippines.  Maritime tensions in the South China Sea continued to be another flashpoint, with a specific incident occurring in August 2025 when two Chinese ships collided while chasing a Philippine boat. There has also been apparent stalling in the negotiation of a Code of Conduct regarding maritime disputes, showing flaws in the regional mechanisms for conflict prevention.  China’s disputes with Taiwan and its maritime disputes show that tension and risk of miscalculation and subsequent escalation are ever-present. 

When it comes to developments in the Korean Peninsula, North Korea has continued to test missiles toward eastern waters, launching two of them in January 2025. One encouraging development when it comes to the two Koreas seems to be that the newly elected president of South Korea, Lee Jae-myung, has a new approach, with a more concilatory policy that has put emphasis on restoring dialogue as well as reducing hostile acts. One particular example of a confidence-building act was Seoul shutting off its loudspeaker propaganda broadcast along the border in June 2025. 

A key trend in East Asia’s security development is military modernisation and rising military budgets. China’s continued assertiveness is definitely an important component of this. China’s defence budget in 2025 is estimated to be $245 billion. China is persistent on modernising its military, with examples such as naval expansion, hypersonic missile development and inclusion of AI warfare. The military parade that took place in Beijing in May 2025 is also a striking example of China wanting to showcase its prowess and capabilities.  China, however, is not the only country in the region expanding its military capabilities. Japan has also taken significant steps, accelerating the deployment of Type‑12 anti‑ship missiles and investing in unmanned systems. North Korea has also continued to modernise its navy. The tendency to ramp up military budgets does not help ease any friction, making efforts of de-escalation and desecuritisation harder to accomplish.  

Main securitised issues in the region include borders and maritime disputes, ballistic missile proliferation and emerging cyber and space threats. The technological advancements that have been made recently have created an entirely new set of problems for countries to deal with, with inclusion of the cyber sphere and AI-powered technology and warfare in the roster of things that can be used. China, in particular, has been accused by other countries of cyber attacks. The use of newer technology, but especially AI is largely unregulated by international law and it is yet to be seen how countries will continue to use it, but considering that East Asia, as a region, has been a hub for tech development and a pioneer in advancements, it will definitely be important and something that countries will have to know how to navigate. The spillover into the cyber sphere shows yet another aspect of the broadening of security. 

When it comes to evolving alignments in East Asia, there has been a tightening of trilateral security cooperation between Japan, South Korea and the US. Japan and South Korea signed the Trilateral Security Cooperation Framework (TSCF) with the US in July 2024. The main goal of this cooperation is to counter the security threat that these countries see in China and North Korea. Another important event for cooperation between Japan and South Korea was the Shangri-La Dialogue, where they cemented their bilateral security ties.  

Amity and Enmity  

The patterns of amity and enmity in East Asia are justified by actors on opposing sides through ideological narratives and stories they tell. Countries like South Korea and Japan narratively present themselves as democracies that have to defend both themselves and the very ideals of democracy from an existential threat. This leads to securitisation, with examples like Japan’s defence white papers explicitly labelling China and North Korea as existential threats. On the flipside, China and North Korea tell narratives of themselves as countries that have to defend themselves from Western influence and the allies of the US. In narratives told by China, Japan is „stirring up tensions“, and the Philippines is engaging in „provocative acts“ and „conducting a dangerous approach“, whereas China describes its own actions as actions that are in accordance with both domestic and international law and „justified response“ or „professional and restrained response.“ 

A very significant and unique part of  East Asia’s security architecture is its regional organisations and forums. East Asia’s web of regional organisations is dense and overlapping, and regionalism in East Asia is characterised by a uniquely informal and personal approach, often called the ASEAN way. The centre of regional cooperation has always been ASEAN, founded by Indonesia, Malaysia, the Philippines, Singapore, and Thailand, and later developing deeper ties with China, Japan and Korea, through initiatives such as ASEAN+3. The most important forum for political and security cooperation that exists in East Asia is the ASEAN Regional Forum, where participants are not only countries in the region but also the US and the EU. The cited goals of this forum are to foster constructive dialogue and consultation on political and security issues of common interest and concern, and to make significant contributions to efforts towards confidence-building and preventive diplomacy in the Asia-Pacific region. Even though ASEAN remains a significant factor and it has its role in regulating internal security relations within the region, its role is also hindered by the influence and interests of great powers, but also divergent interests within ASEAN.  

An important thing to note about East Asia is that institutional means of creating dialogue and finding solutions together in a truly inclusive and multilateral way have been very difficult. Six Party Talks, Shangri-La dialogues and cooperation within ASEAN have all left a lot of issues unresolved. Despite that, certain improvements in the area of multilateral cooperation have been made. For example, China has managed to sign multilateral agreements with countries that it considers itself close to, but also countries that it has complicated relationships with, predominantly in the area of maritime regulation, but also land and air domains. This includes Brunei, Cambodia, India, Indonesia, Japan, the Philippines, Singapore, Thailand and Vietnam.  

Interregional and Global Dynamics 

From an interregional perspective, there are deeply woven links between East Asia and South Asia, particularly through the China-Pakistan economic corridor (CPEC) and China’s border disputes and maritime competitiveness with India. The Belt and Road initiative has also helped China extend its reach into Central Asia and Southeast Asia. Regional security and interdependence in East Asia have also been undeniably shaped by the most important actors globally. The dynamic between China and the US and their rivalry on the international scene affects the security architecture of the entire region. China’s rise and influence have been very worrying to the US for a long time, and it has been of great importance to the US to counter that successfully. According to the white paper on National Security published by China’s State Council Information Office in 2025, China’s goal is to pressure the United States and other nations to reduce or cease lawful operations near areas Beijing claims territorial sovereignty over. The US has managed to deeply penetrate the region through military bases as well as its economic influence. It has also cemented its presence in the region through strategic alliances with countries in the region. The alliance that the US has with Japan and South Korea, but also the alliances that Russia and Iran have with China and North Korea, are shaped first and foremost by having common enemies. 

Buzan and Waver characterised East Asia as a multipolar but US-dominated security complex, with a clear internal structure, anchored by major powers like China, Japan, and the Koreas, and strong external penetration by the United States. This description of the regional structure remains relevant, as well as the analysis of tensions regarding the Korean Peninsula and the maritime disputes. A crucial change is that China can now fully be described as the US’s biggest competitor that aims to change norms and institutions rather than fit into an already existing world order. ASEAN also remains an important infrastructure for multilateralism and cooperation; however, it has proven to be ineffective in resolving tensions in the region that are acute. The trend of opposing trilateral strategic alliances (Japan-South Korea-US and China-North Korea-Russia) is likely to continue, keeping the region polarised. Flashpoints like Taiwan and the South China Sea are going to remain dominant in the discourse and geopolitics. On the other hand, with recent developments regarding US tariffs and China’s response, it seems that the economic arena is the way that rival countries choose to go back and forth. The US tariffs could have an impact on the US influence in the region as a whole.  

Conclusion  

East Asia is a region where rising power competition and enduring territorial disputes, and fragile conflict-management mechanisms coexist with a strong desire for stability and economic interdependence. This creates a composite picture of one of the most strategically relevant, but also potentially volatile regions in the world. Its success in development and deep economic ties have not succeeded in neutralising destabilising factors or finding means and strategies to work together between countries in creating a more stable region. The risk of miscalculation and escalation is constant while maritime incidents increase, military modernisation accelerates, and diplomatic alignments shift. It shouldn’t be left unremarked, however, that the region has also shown resilience and effort through multilateral forums, crisis-communication efforts, and growing awareness of shared vulnerabilities such as economic shocks, natural disasters, and technological disruptions.  

East Asia’s future security trajectory will depend on whether regional actors can strengthen cooperative mechanisms within this complex, mitigate great-power rivalry, and prevent localised disputes from escalating. There will also need to be a balance between deterrence and diplomacy, national interests and collective responsibility and competition and cooperation. The thing that is going to determine both the region’s structure and the movement of the global tectonic plates is how rivalries are handled and how China’s position continues to develop, and if someone, if anyone, can counter it. Looking at interdependence within the region and just how closely entwined issues are makes it obvious why the regional level is an important one to grasp. RSCT is an especially relevant theory for understanding both how these regional threats have developed and why they continue to persist.  

References: 

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