Japan Deepens Security Ties with Key Southeast Asian Partners

Japan is strengthening its defence ties across Southeast Asia, deepening security partnerships with nations that share similar concerns about regional stability in the Indo-Pacific. Recent developments with Indonesia, the Philippines, Vietnam, and Singapore highlight Japan’s evolving role as a regional security partner—particularly in maritime defence, capability building, and countering disinformation.

Japan–Indonesia Maritime Cooperation

Indonesia faces persistent maritime security challenges, especially around the North Natuna Sea, where China’s expansive claims overlap with Indonesia’s Exclusive Economic Zone. Frequent incursions by Chinese vessels have led to heightened tensions, with Indonesian fishermen increasingly blocked from traditional fishing grounds.

Japan has responded by supporting Indonesia’s maritime security through both financial and technical assistance, including potential co-development of Japan’s Mogami-class frigates. Under this arrangement, four vessels would be built in Japan and four in Indonesia, enabling transfer of naval technology and production know-how. Additionally, discussions are underway regarding the possible transfer of decommissioned Soryu-class submarines from the Japan Maritime Self-Defense Force (JMSDF), although this has not been confirmed.

Japan is also supplying high-speed patrol boats under its Official Security Assistance programme and funding the construction of an Offshore Patrol Vessel for the Indonesian Coast Guard. These efforts aim to bolster Indonesia’s maritime patrol capabilities and reflect a shared commitment to preserving regional maritime order.

A bilateral forum for defence practitioners has also been established, focusing on equipment transfers, joint maritime operations, and technology exchange. This institutional framework reinforces the interoperability of the two countries' maritime forces.

Japan–Philippines Strategic Partnership

In March 2025, Philippine Defence Secretary Gilberto Teodoro Jr. met JMSDF Chief of Staff Admiral Saito Akira in Manila. Their discussions centred on countering Chinese disinformation and strengthening defence cooperation. Japan has supplied the Philippines with advanced military radars and continues to explore joint production of defence equipment tailored to Philippine needs.

A major development in the relationship is the Reciprocal Access Agreement (RAA), which will allow for more seamless joint exercises and defence coordination. The agreement also supports disaster response cooperation and high-level exchanges.

On the maritime front, Japan has provided ten 44-metre class patrol boats and two 97-metre class multi-role response vessels (MRRVs) to the Philippine Coast Guard, with five additional MRRVs scheduled for delivery in 2027.

Japan–Vietnam Comprehensive Engagement

Japan’s ties with Vietnam extend beyond defence into broader strategic cooperation. During a recent visit by Prime Minister Shigeru Ishiba, both countries agreed to deepen political trust and defence collaboration while expanding cooperation in science, technology, and economic development.

Vietnam highlighted Japan’s pivotal role as its largest Official Development Assistance (ODA) donor, contributing over ¥3 trillion (US$20 billion), or around 30% of total ODA received. This funding supports key infrastructure and capacity-building projects. Vietnam has requested Japan’s continued involvement in major infrastructure development and praised efforts to streamline ODA processes for greater efficiency.

At the same time, Vietnamese leaders proposed designating science and innovation as a new pillar of bilateral relations. Key areas identified for cooperation include digital transformation, human resource development, labour mobility, high-tech agriculture, and clean energy. These initiatives underscore Japan’s multidimensional engagement with Vietnam, combining security interests with long-term socio-economic development.

Japan–Singapore Practical Security Ties

Singapore plays a strategic role in Japan’s Southeast Asia policy, given its status as a maritime hub and consistent advocate for a rules-based regional order. The two countries maintain close defence ties, anchored by regular Self-Defense Force port calls and naval exercises.

In April 2023, the Japanese and Singaporean navies conducted a passage exercise in the South China Sea, contributing to regional interoperability. Although details remain limited, both sides have held discussions on further enhancing defence cooperation, signalling an interest in deepening engagement.

Strategically, Singapore and Japan are aligned in their support for a free and open Indo-Pacific, based on international law. Amid rising tensions in the South China Sea and Taiwan Strait, Singapore recognises that collective security efforts, including those involving Japan, are essential to preserving stability.