Deepening Maritime Cooperation among Japan, the United States, and the Philippines: The New Security Structure Indicated by the Bashi Channel Exercises

From February 20 to 26, 2026, a multilateral maritime cooperation activity (MMCA) involving Japan, the United States, and the Philippines was conducted within the Philippine exclusive economic zone. This exercise is noted as an important case demonstrating a qualitative transformation in security cooperation in the Indo-Pacific region. According to an official announcement from the U.S. Indo-Pacific Command, this exercise is the second MMCA of 2026, following a trilateral exercise involving Australia, the Philippines, and the United States. These continuous multilateral cooperations go beyond mere routine exercises and reflect a structural change in the regional security architecture.

The tactical focus of this exercise was on enhancing interoperability in fundamental maritime operational capabilities, such as replenishment at sea (RAS), carrier-based aircraft landing qualifications, and communication training. Additionally, expert exchanges on the ground at Subic Bay included training on visual information management, air operations, and navigation, aiming to deepen cooperation from both practical exercises and knowledge transfer perspectives. Colonel Dave Fuljack, commander of the U.S. Navy's 15th Destroyer Squadron, stated in a declaration, "We are prepared to face any challenges to regional security together, building on the bonds we have forged over decades," emphasizing that this cooperation is not temporary but part of a long-term strategic partnership.

The Bashi Channel, where this exercise was conducted, is strategically located between Taiwan and the Philippines' Luzon Island, connecting the western Pacific and the South China Sea. As the Chinese Navy aims to expand into the Pacific, this channel becomes one of the key chokepoints for breaking through the first island chain. The participation of Japan's Maritime Self-Defense Force with P-3C patrol aircraft in this exercise clearly indicates that Japan's security interests are expanding beyond the East China Sea and surrounding waters to the northern South China Sea. This signifies a geographical expansion of the U.S.-Japan alliance's response to China's maritime advances.

Since the beginning of 2026, the Japanese government has also reached an important milestone in the qualitative enhancement of its defense capabilities. According to reports from the U.S. Naval Institute News, the Japan Maritime Self-Defense Force's Aegis destroyer "Chokai" (DDG-176) is expected to acquire the operational capability for Tomahawk cruise missiles within 2026, becoming the first vessel to possess long-range stand-off attack capabilities at sea. This concretizes the counterstrike capability (enemy base attack capability) indicated in the 2022 revision of the national security strategy and marks a historic turning point in Japan's defense policy. However, as pointed out by the Center for Strategic and International Studies (CSIS), there remains the challenge that the operational coordination process for this long-range attack capability has not yet been established between Japan and the United States.

The security environment in East Asia is intensifying pressure on Japan from multiple directions. North Korea conducted ballistic missile launch tests on January 4 and January 27, 2026. According to announcements from the Japanese Ministry of Defense, the two missiles launched on January 4 reached an altitude of approximately 50 kilometers and flew 900 kilometers and 950 kilometers, respectively. Although these missiles fell outside Japan's exclusive economic zone, they demonstrate the capability to cover the entire Japanese territory. Furthermore, North Korea conducted training for launching cruise missiles capable of reaching Japan on December 28 of the previous year, diversifying the threat to Japan from both ballistic and cruise missiles.

On the other hand, in the East China Sea, China is accelerating resource development activities. The Japanese Ministry of Foreign Affairs confirmed on January 16, 2026, that China had begun constructing new structures on its side of the Japan-China median line and lodged a protest. Additionally, on January 2, it was confirmed that China had moored and fixed a mobile drilling vessel in the same area, prompting Japan's Coast Guard to issue a navigation warning. These movements, coupled with the intensified activities of Chinese government vessels around the Senkaku Islands, are heightening tensions between Japan and China in the East China Sea.

In response to these multifaceted security challenges, Japan is adopting a strategy to diversify and multilayer its cooperation with allies and regional partners. While centering on the U.S.-Japan alliance, Japan is deepening defense cooperation with the Philippines and building a multilateral framework that includes Australia, thereby preparing to address both China's maritime expansion and North Korea's nuclear and missile threats. This strategic approach is creating a new regional security structure that treats the East China Sea and South China Sea—two critical maritime security frontlines for China—as a single interconnected theater, as noted by the diplomatic magazine "The Diplomat."

However, this deepening of cooperation also comes with political and financial challenges. As highlighted in a report by the Asia Society, the Special Measures Agreement (SMA) regarding the costs of U.S. military presence in Japan is scheduled for renegotiation in 2026, and the issue of cost-sharing could impact the future development of the U.S.-Japan alliance. Additionally, the establishment of an operational coordination mechanism between Japan and the United States, associated with Japan's possession of long-range attack capabilities, is urgent. Furthermore, deepening cooperation with the Philippines means increasing Japan's involvement in South China Sea issues, which could bring new tensions to diplomatic relations with China.

What has become evident in 2026 is that Japan's security policy is shifting from passive, defense-oriented strategies to active contributions to regional security. The deployment of Tomahawk-equipped vessels, participation in exercises in the Bashi Channel, and the institutionalization of multilateral cooperation with the Philippines and Australia all embody this strategic transformation. This is not merely a change in Japan's policy but a result of the convergence of the expansion of Japan's role in the U.S. Indo-Pacific strategy and the rising concerns of regional countries regarding China's maritime advances.

Looking ahead, a key point of interest will be to what extent this trilateral cooperation becomes institutionalized and establishes itself as a framework for permanent security cooperation. If multiple MMCA exercises are conducted throughout the year, joint training is advanced, and capabilities for joint responses in emergencies are improved, a new pillar of security order in the Indo-Pacific region will be formed. In that sense, the Bashi Channel exercise in February 2026 should be recorded not merely as a single exercise but as a historic step symbolizing structural changes in regional security.