New Developments in Japan-U.S.-Philippines Maritime Cooperation: Structural Changes in Security Indicated by the Bashi Channel Exercises

From February 20 to 26, 2026, the Philippine military, the Japan Maritime Self-Defense Force, and the U.S. Indo-Pacific Command conducted the 15th Multinational Maritime Cooperation Activity (MMCA) within the Philippine Exclusive Economic Zone in the West Philippine Sea (South China Sea). This exercise is noteworthy as it symbolizes a structural change in the security architecture of the Indo-Pacific region, going beyond mere routine training.

The Bashi Channel, the stage for the exercise, is a strategic chokepoint that separates Taiwan from Luzon Island in the Philippines. This maritime area is an important route connecting the Western Pacific and the South China Sea and is one of the main routes for the Chinese Navy to access the Pacific. The Japan Maritime Self-Defense Force dispatched P-3C patrol aircraft to conduct flight training in cooperation with the U.S. military and the Philippine military. The P-3C excels in anti-submarine patrol capabilities and plays a crucial role in monitoring submarine activities in this area.

The significance of this exercise lies particularly in its timing and geopolitical context. February 2026 is a period during which Japan's security policy is undergoing a major shift under Prime Minister Sanae Takaichi, and it is also the year the Philippines serves as the ASEAN chair. Japan is moving away from post-war pacifism and transforming into a more proactive security partner. The new national security strategy approved by the Kishida Cabinet in December 2022 serves as the foundation for this change.

The deepening cooperation among the three countries is progressing on multiple levels. First, there is an improvement in interoperability at the operational level. In this MMCA, integration of communication systems, coordination of search and rescue operations, and sharing of maritime surveillance information were implemented. Through the accumulation of such training, rapid joint responses in emergencies become possible. Second, there is a sharing of awareness at the strategic level. The three countries share a common goal of maintaining a "rules-based international order" and are united in their opposition to unilateral changes to the status quo through coercion or force.

In the context of the Japan-U.S. alliance, this trilateral cooperation indicates a new phase. The U.S. under the Trump administration has been demanding greater defense burdens from its allies. In response, Japan is advancing significant increases in defense spending and the acquisition of counterstrike capabilities (capabilities to attack enemy bases). Furthermore, the massive $550 billion commitment to investment in the U.S. suggests a new form of alliance that integrates economics and security. Japan is not merely receiving U.S. protection but is taking on a role as an active security player in the Indo-Pacific region.

For the Philippines, this trilateral cooperation is also strategically important. The Marcos administration is strengthening international partnerships to counter China's claims in the South China Sea. In addition to the Mutual Defense Treaty with the U.S., by deepening defense cooperation with Japan, the Philippines is aiming to diversify its deterrent capabilities. This exercise demonstrates that the Philippines is acting as a member of a regional security network rather than confronting China alone.

From China's perspective, this trilateral cooperation is clearly a cause for concern. The exercises in the Bashi Channel signify an enhancement of capabilities to monitor and constrain the Chinese Navy's access to the Pacific. Moreover, Japan's shift in security policy, particularly regarding the acquisition of counterstrike capabilities and the consideration of introducing nuclear-capable submarines, has raised alarm, prompting the Chinese Foreign Ministry and Ministry of Defense to denounce it as a "serious challenge to the post-war international order." The diplomatic crisis between China and Japan from late 2025 to early 2026 reflects this tension.

Looking ahead, this trilateral cooperation is likely to become further institutionalized. In the bilateral strategic dialogue between the U.S. and the Philippines, there has been an agreement to hold policy dialogues at the foreign minister level involving Japan and other countries. Additionally, there is a prospect of expanding cooperation to include South Korea. The U.S. and South Korea are scheduled to conduct large-scale joint military exercises called "Freedom Shield" from March 9 to 19, 2026, and if defense cooperation between Japan and South Korea progresses, a broad regional security network connecting Northeast Asia and Southeast Asia may be formed.

However, there are challenges to this cooperation. First, there is the management of relations with China. Excessive military pressure could heighten regional tensions and increase the risk of unintended conflict. Second, there is the need to maintain political support within each country. In Japan, there is domestic backlash against changes in constitutional interpretation, and in the Philippines, there are differing opinions regarding China policy. Third, there is the sustainability of U.S. commitment. Under the Trump administration's "America First" policy, allies feel uncertainty about the long-term maintenance of U.S. engagement.

Nevertheless, the recent exercises in the Bashi Channel demonstrate a new standard for security cooperation in the Indo-Pacific region. Japan, the U.S., and the Philippines are advancing the construction of an effective maritime security system while harmonizing their respective national interests and the common goal of regional stability. This movement is likely to expand the strategic options for small countries in an era of great power competition and serve as a crucial element in promoting the multipolarity of regional order.