The New Phase of South China Sea Security Indicated by the Joint Exercises of Japan, the United States, and the Philippines: Deployment to the Bashi Channel and China's Response

The 15th Multinational Maritime Cooperation Activity (MMCA), conducted from February 20 to 26, 2026, marked a significant turning point in the security cooperation among Japan, the United States, and the Philippines. This exercise is particularly noteworthy because the operational area expanded significantly northward from the traditional waters around Scarborough Shoal to areas off the northernmost Batanes Islands of the Philippines, and even approached the Bashi Channel. This geographical expansion symbolizes a qualitative change in the security strategy in the Indo-Pacific region, going beyond mere enlargement of the exercise scale.

The exercise involved the Philippine Navy's Jose Rizal-class frigate "Antonio Luna," the Philippine Coast Guard's multi-role response vessel "Gabriela Silang," and the U.S. Navy's Arleigh Burke-class guided-missile destroyer "Dewey," which conducted joint operations at sea. From the air, Japan's Maritime Self-Defense Force P-3C patrol aircraft and the U.S. Navy's P-8A Poseidon conducted flight training, enhancing the integrated operational capabilities of air and sea forces. The exercise included a wide range of activities such as communication training, maritime situational awareness, anti-submarine warfare, and live-fire training, significantly strengthening interoperability among the three countries.

The Bashi Channel is a strategic chokepoint that separates Taiwan and the Philippines and is one of the main shipping routes connecting the Western Pacific and the South China Sea. Conducting exercises in this area clearly demonstrates the willingness of Japan, the U.S., and the Philippines to engage in maintaining maritime order not only in the South China Sea but also in the broader First Island Chain. Captain Jennifer Monforte of the Philippine Navy emphasized that the exercise's proximity to the Bashi Channel was "a planned exercise conducted within the Philippines' exclusive economic zone. Since it is not in the waters of other countries, it does not constitute a provocative act." However, the choice of this geographical location clearly reflects a new reality in the regional security environment.

China's response was predictably strong. During the exercise, the People's Liberation Army Navy deployed the Jiang Kai II-class missile frigate "Liuzhou 573" and the Type 052C destroyer "Hefei 174," continuously tracking the vessels of Japan, the U.S., and the Philippines. Notably, Hefei 174 continued to track the three countries' vessels from the waters around Scarborough Shoal to the northern waters of the Batanes Islands. Captain Monforte pointed out, "The presence of Chinese naval vessels in the Batanes area is abnormal. They usually remain around Scarborough Shoal," highlighting the unusual nature of China's surveillance activities. A spokesperson for the Southern Theater Command of the Chinese military announced on February 26 that "China conducted regular patrols in the South China Sea from February 23 to 26," condemning the Philippines for organizing joint patrols with foreign countries as "disrupting peace and stability."

An even more serious issue arose when the Philippine Coast Guard announced on February 23 that it had experienced signal jamming from China while conducting maritime patrols around Scarborough Shoal. According to Coast Guard spokesperson Jay Taliera, the Starlink connection of the Bureau of Fisheries and Aquatic Resources vessel and the Coast Guard's MRRV 4409 was lost. "There have been repeated incidents of signal loss within 24 nautical miles of Scarborough Shoal, especially when approaching, leading us to believe that China is conducting signal jamming," Taliera stated. The use of electronic warfare capabilities poses new concerns for maritime security, as it jeopardizes communication delays and inter-vessel communications.

The strategic significance of this exercise needs to be understood on multiple levels. First, the northern expansion of the exercise area indicates that the security cooperation among Japan, the U.S., and the Philippines is not limited to specific areas in the South China Sea but aims to maintain a broader maritime order. The Bashi Channel occupies an extremely important strategic position in regional crises, including a Taiwan contingency, and joint exercises in this area suggest the potential for cooperation in times of emergency.

Second, this exercise reflects the evolution of Japan's security policy. The participation of the Maritime Self-Defense Force's P-3C patrol aircraft demonstrates Japan's intention to play a more proactive role in regional security, moving beyond its traditional framework of exclusively defensive defense. In the revised National Security Strategy and Defense Build-Up Plan of 2023, Japan has prioritized strengthening the defense of the southwestern islands and deepening cooperation with allies and like-minded countries, making this exercise a concrete implementation of that policy.

Third, the change in the Philippines' strategic choices is notable. Despite emphasizing dialogue with China following the 2016 arbitration ruling, the Philippines has significantly strengthened its security cooperation with the U.S. and Japan in response to China's coercive actions in the South China Sea in recent years. On February 11, 2026, the first coastal surveillance radar system was delivered to the Philippines under Japan's Official Security Assistance (OSA) framework, deepening defense cooperation in terms of equipment.

China's response will be a crucial factor influencing the future regional security environment. The tracking of vessels during the exercise, the use of signal jamming, and diplomatic condemnation indicate that China perceives the deepening cooperation among the three countries as a significant challenge. However, it is also noteworthy that China did not resort to military force in response to these activities. This suggests that, at this stage, China is adopting a strategy of deterring the progress of trilateral cooperation through diplomatic and military pressure.

The maritime cooperation among Japan, the U.S., and the Philippines is expected to become further institutionalized, with an increase in the frequency and scale of exercises. The U.S. emphasizes multilateral cooperation with allies and partner countries as part of its Indo-Pacific strategy, and there is potential for development into larger-scale exercises involving countries such as Australia and South Korea. For Japan, the defense of the southwestern islands and stability in the waters around Taiwan are core issues of national security, making cooperation with the Philippines and the U.S. essential. For the Philippines, building effective deterrence against China's maritime expansion is an urgent task.

The expansion of exercises into the Bashi Channel symbolizes that the security order in the Indo-Pacific has entered a new phase. The deepening cooperation among Japan, the U.S., and the Philippines is a crucial effort to deter China's unilateral changes to the status quo and maintain a maritime order based on the rule of law. At the same time, it cannot be denied that this cooperation may heighten regional tensions and increase the risk of military confrontation. The key moving forward will be how to balance the two trajectories of strengthening deterrence and maintaining dialogue. The 15th MMCA vividly illustrates the realities of the regional security environment facing this challenging task.