Chinese Navy vessels navigate unprecedentedly in Japan's southwestern waters—A warning to Taiwan or the normalization of breaking through the first island chain?

In the third week of April 2026, naval vessels of the People's Liberation Army (PLA) passed through international waters around Japan's southwestern islands twice, creating new tensions in the East Asian security environment. The 133rd Fleet, which passed through the Yokoate Channel on April 19 heading towards the Pacific, returned on April 22 via the Yonaguni-Iriomote Channel located between Yonaguni Island and Iriomote Island. Yonaguni Island, the westernmost island of Japan, is located just 110 kilometers from Taiwan, and this is the first time that PLA vessels have been publicly recorded as navigating through this channel.

The Eastern Theater Command stated in a declaration on April 22, "The 133rd Fleet has completed training exercises in the Western Pacific and returned via the Yonaguni-Iriomote Channel. This effectively verifies the unit's long-range operational capabilities." The emphasis on "long-range operational capabilities" suggests that operational actions in the high seas beyond the First Island Chain are no longer exceptional but are becoming normalized.

Military analyst and former PLA instructor Song Zhongping evaluated this passage as "a clear warning to Japan." The background to this is Japan's increasing involvement in the Taiwan issue year by year. Since the Kishida administration, Japan has significantly shifted its security strategy, explicitly stating in the national security strategy adopted by the cabinet in 2022 that peace and stability in the Taiwan Strait are "extremely important for Japan's security." The policy to increase defense spending to 2% of GDP, the deployment of missile defense units to the southwestern islands, and the deepening of the Japan-U.S. alliance appear to Beijing as preparations for "intervention in the Taiwan issue."

Since 2016, the Japan Ground Self-Defense Force has stationed a coastal surveillance unit on Yonaguni Island, monitoring the movements of vessels and aircraft in the Taiwan Strait and the East China Sea through radar facilities. The fact that PLA vessels passed close to this surveillance network can be interpreted as China deliberately "showing off" its awareness of Japan's intelligence-gathering capabilities. In other words, it is a declaration of intent to act with the understanding that they can be monitored, and even to operate under the premise of being observed.

This movement is not an isolated incident. Around the same time, China's first Type 076 amphibious assault ship, the "Sichuan," departed from Shanghai and entered trial voyages towards the South China Sea. The Type 076 is estimated to have a full-load displacement of about 40,000 tons and is designed with electromagnetic catapults, differing from traditional amphibious assault ships, and is specialized for drone operations. The official Weibo account of the Chinese Navy explained that this is a "regular test training to verify the performance of multiple onboard systems and platforms," but the timing coinciding with U.S.-Philippine-Japan joint exercises is hard to dismiss as mere coincidence.

Furthermore, prior to the departure of the Type 076, Taiwan's Ministry of National Defense confirmed that China's first aircraft carrier, the "Liaoning," passed through the Taiwan Strait heading towards the South China Sea. Photos released by Taiwan show eight J-15 fighter jets and three helicopters on the flight deck of the Liaoning. The simultaneous occurrence of the aircraft carrier, the drone-equipped amphibious assault ship, and fleet navigation around the southwestern islands indicates that the Chinese Navy is enhancing its multi-axis simultaneous deployment capabilities.

The movements of U.S. forces in Okinawa are also noteworthy. The U.S. Navy is conducting large-scale joint exercises in the South China Sea with the Philippines and Japan, and there are views that China's "response" to these exercises is the fleet's navigation through the southwestern islands and the aircraft carrier's passage through the Taiwan Strait. The simultaneous military actions of both the U.S. and China in the same maritime area evoke memories of U.S.-Soviet naval confrontations during the Cold War and carry the risk of accidental conflict.

The Japanese government's response has been cautious. The Ministry of Defense continues to track and monitor PLA vessels with Japan's Maritime Self-Defense Force escort ships and patrol aircraft, but has not made any official protests. The navigation through international waters itself falls within the rights of freedom of navigation under international law, and there are no legal issues. However, in a strategic context, the fact that China is gradually expanding its military presence around Japan's southwestern islands cannot be ignored.

Particularly concerning is the increasing frequency of such passages. Since 2025, the navigation of PLA vessels through the Osumi Strait, Tsugaru Strait, and Miyako Strait has already become routine, but the exploration of new routes like the Yonaguni-Iriomote Channel suggests that the Chinese Navy is deepening its understanding of Japan's maritime traffic routes and seeking more options. In the event of a Taiwan contingency, the waters surrounding Japan's southwestern islands hold significant importance as both supply routes and retreat routes.

Several options can be considered for Japan's response. First, further strengthening of the defense posture of the southwestern islands. This could include the enhancement of missile units stationed on Yonaguni Island, Ishigaki Island, and Miyako Island, as well as the new deployment of electronic warfare units. Second, deepening information sharing between Japan and the U.S. and improving wide-area surveillance capabilities through the introduction of maritime surveillance drones. Third, expanding informal security cooperation with the Philippines and Taiwan. However, excessive responses could reinforce China's narrative of an "encirclement" and carry the risk of escalating tensions.

The maritime security environment in East Asia has entered a new phase in 2026. The PLA's breakthrough of the First Island Chain is no longer "news," and the responses of the U.S. and its allies are becoming "news." Japan, positioned geographically at the forefront, faces the dual challenge of strengthening deterrence and avoiding escalation of tensions. The recent navigation of PLA vessels has once again highlighted this difficult balance.