By Lu Hao

During the recent ASEAN Summit, the leaders of Japan and the Philippines met and emphasized their commitment to further strengthening economic and security cooperation, announcing their agreement to sign the Acquisition and Cross-Servicing Agreement (ACSA). This marks another major step in bilateral military and defense collaboration following the entry into force of the Reciprocal Access Agreement (RAA) between the two countries.  

Notably, once the new agreement is signed, the Japan–Philippines defense cooperation framework will fully cover areas such as defense strategy, military tactics, intelligence sharing, equipment and technology, and joint training, effectively establishing a "quasi-alliance" between the two nations. Analysts note that the Philippines has become a key lever for Japan to expand its influence within ASEAN, intervene in South China Sea affairs, and advance its so-called strategy of balancing China. These developments warrant close attention from regional countries.

In fact, since the Philippine Aquino III administration established a strategic partnership with Japan in 2011, bilateral engagement has grown increasingly frequent. In recent years, both sides have placed particular emphasis on accelerating the institutionalization of military and defense cooperation as a cornerstone of their bilateral relationship. In 2016, Japan and the Philippines signed the Agreement Concerning the Transfer of Defense Equipment and Technology, making the Philippines the first ASEAN country to establish such cooperation with Japan. In 2022, the two countries held their first "2+2" foreign and defense ministerial meeting, making the Philippines the second ASEAN nation to adopt this mechanism with Japan. In 2023, Japan launched the Official Security Assistance (OSA) framework, designating the Philippines as one of its first recipient countries. In 2024, Japan and the Philippines signed the RAA, facilitating the rapid deployment and joint operations of their respective forces in each other's territory. The newly proposed ACSA goes a step further by allowing the two countries' defense forces to provide each other with logistical support, such as fuel, food, and medical services, during joint military operations and peacekeeping missions. This agreement will serve as a stable framework for the long-term and institutionalized development of Japan–Philippines defense cooperation.

The deepening of Japan–Philippines defense ties is by no means accidental. Since taking office, Philippine President Ferdinand Marcos Jr. has actively sought to strengthen relations with both the US and Japan. For its part, Japan has been working to support Washington's transformation of the US-led Asia-Pacific alliance structure from a "hub-and-spoke" model to a more networked framework, using the so-called Indo-Pacific Strategy as its foundation and focusing on building "US–Japan plus" minilateral partnerships. On one hand, Japan has been assisting the Philippines in enhancing its maritime security capabilities by providing equipment and technical training, and by promoting trilateral naval and coast guard exercises with the US and the Philippines. On the other hand, Tokyo has publicly stated its intent to cooperate with Manila in developing critical and emerging technologies, advancing space security collaboration, and organizing high-level dialogues on cybersecurity and digital issues. Analysts point out that the deepening military coordination among the US, Japan, and the Philippines through enhanced equipment interoperability, expanded intelligence sharing, and strengthened joint maritime intervention capabilities will inevitably heighten regional tensions.

Behind the upgraded Japan–Philippines defense relationship lie distinct strategic calculations. Japan, driven by Washington's strategic guidance and its own competitive mindset toward China, claims to be pursuing a robust diplomatic and security policy. While accelerating its defense buildup, Tokyo continues to court partners across the so-called Indo-Pacific, using them as leverage in its China-containment agenda. The Philippines, meanwhile, seeks external backing to embolden its provocative and unlawful actions in the South China Sea.

The Asia-Pacific region is a key hub for peaceful development rather than an arena for rivalry. Any defense or security cooperation with other countries should not target any third party or meddle in the South China Sea disputes, still less provoke confrontation or escalate tensions in the region. Japan and the Philippines should draw profound lessons from history and abandon the illusion of seeking so-called security through exclusive blocs. Instead, they should take concrete actions to genuinely uphold regional peace and stability.

(The author is the director of the Comprehensive Strategic Studies Division, Institute of Japanese Studies, CASS.)