Authors: Aadityavikram Rana and Gitanjali Sinha Roy*
In departure from its post-war pacifist traditions, Japan is redefining its role in regional security by expanding defence cooperation with Association of Southeast Asian Nations (ASEAN). This adjustment is not only reactive; it represents a proactive, multifaceted strategy influenced by geopolitical changes, especially China’s maritime assertiveness, the instability of U.S. strategic commitments, and Japan’s vision of a Free and Open Indo-Pacific (FOIP). The endgame is not to simply counterbalance China but to anchor a resilient, rules-based security architecture in Southeast Asia.
Japan’s Strategic Evolution
Since Second World War, Japan’s military action has been limited by its Article 9 of the constitution. However, Tokyo has embraced a more secure approach through what it terms as “proactive pacifism” by stepping up its security profile through the 2015 collective self-defence legislation and the 2022 National Security Strategy under late Prime Minister Shinzo Abe. Some of the key milestones achieved are Vientiane Vision (2016), Japan’s first formal defence guideline towards ASEAN that emphasised sovereignty, rule of law and maritime security. JASMINE Initiative that ranges from cybersecurity training to ship-rider deployments, designed to operationalise Japan-ASEAN defence cooperation.
Furthermore, Japan has participated in ADMM-Plus and the ASEAN Regional Forum where it plays a leading role in multilateral security platforms to prioritise dialogue over deterrence. This posture of Japan poses itself as a credible, and trustworthy contributor to collective security and doesn’t arm twist like China.
Why ASEAN?
Change is constant and thus, Japan and the world’s interest is shifting from the west back towards east (specifically Indo-Pacific). ASEAN sits at the intersection of Japan’s economic and strategic interests. Its geographic position, diplomatic balancing and institutional unity makes it an important partner in shaping the Indo-Pacific’s security order.
ASEAN is the centre of Japan’s FOIP vision. A secure and autonomous Southeast Asia ensures open sea, resists great-power monopolisation, and legitimises Japan’s normative agenda anchored in UNCLOS, peaceful dispute resolution, and non-coercive diplomacy. Japan seeks to hedge against American unpredictability by diversifying its security partnerships while the U.S.-Japan alliance remains foundational. ASEAN is central to this diversification, not replace to the U.S., but to enhance and support shared goals more effectively.
Japan’s economic arteries: energy imports, manufacturing bases, and trade routes—flow through ASEAN. Any disruption in the South China Sea would hit Japan’s economy hard. Securing these lifelines is not just a strategic priority; it’s economic self-preservation. China’s expansionism in the South China Sea and the East China Sea are challenges to the rules-based order. Japan, though not a claimant, shares ASEAN’s concerns about Chinese aggression and coercion. With the help of maritime capacity-building, defence equipment’s and naval drills, Japan indirectly supports regional deterrence without provoking China.
Japan is actively investing in ASEAN’s indigenous defence capabilities through a variety approach such as the provision of defence equipment. For example, coastal radar systems, patrol vessels, and surveillance aircraft to important regional partners like the Philippines, Indonesia, and Vietnam. In addition to material support, Japan engages in joint training exercises—both bilateral and multilateral—that focuses on areas such as anti-piracy operations, humanitarian assistance and disaster relief (HADR), and enhancing maritime domain awareness. Furthermore, Japan supports ASEAN nations through cybersecurity initiatives and intelligence-sharing programs aimed at reinforcing digital defences and supporting the strategic advancements.
Japan’s defence outreach to ASEAN is multi-dimensional, strategically combining hard security measures with elements of soft diplomacy. One of the key instruments of engagement is the Official Security Assistance (OSA) program, a newly launched initiative that provides non-lethal military aid and capacity-building support to friendly nations, with ASEAN countries being its primary focus. Complementing to this, Japan has relaxed its arms export policies to initiate the transfer of defence technology, resulting in agreements such as the export of radar systems to the Philippines and potential deals involving submarines or aircraft with Indonesia. Japan also regularly engages in joint military exercises with ASEAN partners, particularly in areas like anti-piracy operations, disaster response, and maritime surveillance. These efforts are underpinned by institutionalised security dialogues, including the Japan-ASEAN Comprehensive Security Dialogue, and participation in multilateral platforms such as the ASEAN Defence Ministers’ Meeting Plus (ADMM-Plus), which enhance strategic alignment. Additionally, Japan promotes techno-strategic cooperation by organising digital law seminars, conducting cyber defence training, and collaborating on joint research and development projects in emerging domains like space situational awareness.
Unlike more coercive powers, Japan frames its defence engagement through norms: transparency, mutual respect, and international law. Initiatives like the Professional Airmanship Program or the Japan-ASEAN Cyber Law Seminar promote shared values while avoiding the optics of militarisation.
This norm entrepreneurship helps Japan socialize ASEAN military establishments into a multilateral, rules-based ethos. It is not just about building armies; it’s about building trust.
One has to understand that Japan was earlier very close to the ASEAN countries and over a period of time, China has been able to take that place from Japan by using chequebook diplomacy, development of infrastructure, diaspora is being leveraged and more influence of China in internal matters of ASEAN countries including their elections in some cases.
Challenges
Japan’s defence cooperation with ASEAN is not without its challenges and limitations. One key obstacle is the internal divergence within ASEAN itself—countries such as Cambodia and Laos maintain closer ties with China, making it difficult for the bloc to reach a unified strategic consensus.
On the domestic front, Japan faces its own set of constraints, including constitutional limitations and a cautious public opinion that restrict how far Tokyo can extend its military engagement. Additionally, China’s significant economic influence in the region poses a dilemma for many ASEAN nations, as their deep economic interdependence with Beijing makes overt strategic alignment with Japan a potentially risky move. Japan on the other hand has been going through the fourth decade of economic burst making it difficult for the economy of Japan to function in many cases.
Finally, Japan’s ambitions are tempered by resource limitations, as the effort to expand defence aid abroad must be balanced against the need to maintain military readiness and fiscal responsibility at home.
The Endgame and future possibilities
Japan’s strategic vision for ASEAN is clear yet deliberately nuanced, reflecting its preference for stability over domination. Rather than seeking to militarize or assert control over the region, Japan aims to empower ASEAN by fostering a security-aware, pro-Japan partnership model—developing strategic partners instead of dependent clients. Central to this approach is Japan’s aspiration to be viewed as a trusted security provider, one whose consistent and restrained behaviour distinguishes it from China’s assertiveness and the perceived unpredictability of the United States. Japan embeds deterrence within a multilateral framework, consciously avoiding exclusive alliances to preserve regional inclusivity and prevent bloc-based polarization. This vision is also anchored in Japan’s interest in securing economic and maritime stability, recognizing that a secure ASEAN directly supports its own economic and energy interests. Ultimately, Japan’s commitment to a rules-based international order—advanced through its Free and Open Indo-Pacific (FOIP) strategy and institutional engagement—underscores its dedication to preserving the normative foundations of peace and cooperation in Asia.
Given the present situation of crisis between Thailand and Cambodia, where Cambodia is being backed by China. It is essential that ASEAN countries need to work on stabilising the regional environment given the stakes to be so high.
There is a need to pave the way for future possibilities, and they are as follows:
- At present, Japan is providing OSA to only a few ASEAN countries like Philippines, Malaysia, and Indonesia and this needs to be expanded to other ASEAN countries. This would help create a network of Japan’s OSA in all the ASEAN countries and help Japan regain its earlier bond with these nations but must consider looking at the countries like Laos and Cambodia which have interests with China.
- 2.If possible, create a maritime fusion centre based on the need to create a centre focusing on information sharing among the ASEAN countries and this can be developed by countries like Japan and India as India already as its own Information Fusion Centre-Indian Ocean Region.
- 3.In the domain of defence and infrastructure development, Japan should try and support the ASEAN countries for ports development ,increase more training for officials in Japan in the domain of cybersecurity and maritime real time information sharing and help create cyber labs which would help manage and deal with any cyber- attacks on critical port infrastructure and security of navigational routes like protecting the GPS being hacked and thus initiative should be supported by the already existing Japan-ASEAN integration fund for the creation of these cyber lab initiatives. Also, create access to the cyber labs virtually for students to do internships and eventually provide jobs in this domain.
Conclusion
Japan’s deepening defence ties with ASEAN are not a break from its past, but a sophisticated evolution of it. Through a careful mix of hard power, soft power, and diplomatic finesse, Japan is crafting a new model of regional leadership—proactive yet restrained, strategic yet inclusive. In an era of shifting power balances, Japan is not chasing dominance. It is securing relevance. In Southeast Asia’s unfolding security landscape, Japan is not just present—it is indispensable.
*Gitanjali Sinha Roy is an assistant professor at the Jindal School of International Affairs, O.P. Jindal Global University.
