The Strategic Significance of Strengthening Japan-U.S.-Philippines Trilateral Cooperation: The Bashi Channel Exercises and the Transforming Japan-U.S. Alliance

On February 28, 2026, the Japan Maritime Self-Defense Force participated in joint exercises with the Philippines and the United States, dispatching P-3C patrol aircraft to conduct flight training in the Bashi Channel. Strengthening trilateral cooperation in this strategic maritime area located south of Taiwan is of utmost importance as the security environment in the Indo-Pacific region rapidly changes.

The Bashi Channel is situated between Taiwan and Luzon Island in the Philippines, serving as a crucial junction connecting the Western Pacific and the South China Sea. For Japan, this maritime area is a lifeline for energy transport routes from the Middle East, and since the 1980s, the government has permitted the defense of this maritime traffic route within the scope of self-defense. In this exercise, the Philippine Navy deployed Antonio Luna-class frigates, AW159 helicopters, and FA-50 fighter jets, while the United States sent the guided-missile destroyer USS Dewey and P-8 Poseidon patrol aircraft. The diverse training content, including communication training, maritime situational awareness, at-sea replenishment, joint aerial patrol, and formation flying, aimed to enhance trilateral interoperability.

The backdrop of this exercise is the serious diplomatic crisis between China and Japan that has persisted since November 2025. Prime Minister Sanae Takaichi's statement in a parliamentary response that a military attack by China on Taiwan could constitute a "situation threatening Japan's survival" triggered a strong backlash from China. China's Consul General in Osaka, Xue Jian, made threatening posts on social media (later deleted), leading to intense diplomatic exchanges between the two countries. China has implemented comprehensive retaliatory measures, including travel advisories against Japan, a halt on seafood imports, suspension of cultural exchanges, and export restrictions on rare earth elements.

Particularly noteworthy is the escalation of military tensions that occurred from December 6 to 7, 2025. The Chinese Navy's aircraft carrier Liaoning passed through the Miyako Strait, conducting takeoff and landing training for its J-15 carrier-based fighter jets. According to Japan's Ministry of Defense, approximately 100 takeoffs and landings were conducted over the two days. More significantly, on December 6, a J-15 fighter jet illuminated the Japan Air Self-Defense Force's F-15 fighter jets with its fire control radar near the Miyako Strait. Defense Minister Shinjiro Koizumi strongly condemned this action, and the Japanese government lodged a formal protest with China. The U.S. State Department also criticized, stating, "China's actions do not contribute to regional peace and stability." This incident clearly demonstrated that China does not hesitate to use military means for intimidation.

The security challenges Japan faces are not limited to tensions with China. The "America First" policy of the second Trump administration is fundamentally altering the prerequisites of the Japan-U.S. alliance. The U.S. National Security Strategy announced in November 2025 explicitly stated the goal of "building military capabilities to deter aggression anywhere along the First Island Chain," yet President Trump warned NATO allies that the U.S. would not defend countries that do not spend 2% of their GDP on defense. This statement suggests that the U.S. may adopt a similar stance toward its Asian allies, including Japan.

In July 2025, Japan agreed with the United States to reduce the tariff rate on imports from the initial proposal of 25% to 15%. In return, Japan promised to expand investments in the U.S. and purchase U.S.-made defense equipment. However, this agreement does not take the form of a traditional international treaty and lacks a dispute resolution mechanism. If either party determines that the other is not fulfilling its obligations adequately, there is a temptation to withdraw from the agreement.

In such an environment, Japan is being compelled to strengthen its strategic autonomy. As two nuclear-armed nations, China and Russia deepen their cooperation and North Korea advances its nuclear and missile capabilities, Japan is moving forward with strengthening its defense posture, including the introduction of counterstrike capabilities. However, the overwhelming nuclear and conventional forces of the United States remain the ultimate guarantee of stability in East Asia. The Trump administration has prioritized deterrence against China in the Indo-Pacific as a core defense priority, showing interest in maintaining stability to benefit from the region's economic vitality.

Importantly, the strategic interests of Japan and the U.S. still significantly overlap. Addressing China's ambitious domestic and regional agenda, strengthening defense capabilities in a new era of warfare, and securing critical supply chains all require multilateral cooperation. While U.S. support is essential for these efforts, Japan also needs to deepen cooperation with partners such as South Korea, ASEAN countries, Australia, India, Canada, and European nations.

The recent trilateral exercise in the Bashi Channel involving Japan, the U.S., and the Philippines is a concrete manifestation of such multilateral collaboration. The Philippines is directly facing China's coercive actions in the South China Sea and has been asserting its maritime interests in cooperation with multiple countries since 2023. For Japan, defense cooperation with the Philippines is essential for securing strategic depth in the event of a Taiwan contingency and enhancing its sea lane defense capabilities.

To adapt to the rapidly changing international environment, difficult political decisions must be made, including adjusting defense spending levels, reallocating budgets from conventional military platforms to unmanned and AI-enabled systems, and investing in advanced industries. The Takaichi administration's decision to spend a year revising the national security strategy is a wise judgment to allow the public time to confront the new reality.

At the same time, it is also a time to emphasize the importance of diplomatic engagement. Direct communication between conflicting nations can reduce friction, while a refusal to engage in dialogue rarely yields the intended results. Deepening relationships with like-minded partners, particularly many countries in the Global South, will help solidify support for international law and reinforce the principle that attempts to change the status quo by force will not be tolerated. Strong defense, information, and economic capabilities are essential, but diplomacy is necessary to work toward a future with lower tensions and less division.