The Critical Point of Military Tension Between Japan and China: Navigation in the Taiwan Strait, Balikatan Exercises, and a New Phase of Defense for the Southwestern Islands

From April to May 2026, the security environment in Northeast Asia is rapidly transforming. Military tensions between Japan and China are reaching unprecedented levels, with the strategic confrontation over the Taiwan Strait at the center. On April 17, the Japan Maritime Self-Defense Force destroyer "Ikazuchi" transited the Taiwan Strait. This marks the second passage of a Japanese vessel through the strait in the past 10 months, and Beijing's response was far more severe than the last time.

China's Ministry of Foreign Affairs, Ministry of National Defense, and Eastern Theater Command all issued statements warning Japan to "悬崖勒马 (turn back from the dangerous edge)." The PLA-affiliated social media account "Jun Zhengping" accused Japan of "playing with fire," and the Eastern Theater Command announced the start of combat readiness patrols in the East China Sea while dispatching warships near Okinawa. This series of responses suggests that the strategic friction accumulated between Japan and China since Prime Minister Sanae Takaichi stated in November of last year that "if China attacks Taiwan, Japan could cooperate in Taiwan's defense" is reaching a critical point.

The backdrop to this tension is the large-scale multilateral military exercise "Balikatan 2026," taking place in the Philippines. Running from April 20 to May 8, the exercise involves the Philippines, the United States, as well as Japan, Australia, New Zealand, Canada, and France, with a total troop strength of approximately 17,000. Notably, Japan is participating as a formal participant for the first time since the signing of the Visiting Forces Agreement (VFA) with the Philippines. The Japan Ground Self-Defense Force deployed Type 88 anti-ship guided missiles to the Philippines and participated in live-fire exercises alongside the Philippine Marine Corps' BrahMos anti-ship missiles. Furthermore, from April 26 to 29, integrated air defense missile defense training involving the U.S., Philippines, and Japan was conducted for the first time.

China's response was immediate and multifaceted. On April 24, the Southern Theater Command of the PLA announced that a surface task group led by the Type 055 destroyer "Zunyi" conducted exercises in the waters east of the Luzon Strait. This task group consists of one Type 055 destroyer, one Type 052D destroyer, one Type 054A frigate, and one Type 903A supply ship. Additionally, the aircraft carrier "Liaoning" was reported to have transited south through the Taiwan Strait on April 20, operating in the South China Sea with three destroyers and six frigates. Moreover, the Chinese military released footage of a launch test of the YJ-20 hypersonic anti-ship missile, showcasing its military presence in the South China Sea.

This pattern of response from China is similar to when the aircraft carrier "Shandong" was deployed east of Luzon during the Balikatan exercise in 2025, but the scale and intensity have clearly escalated. Beijing's backlash against Japan's initial participation is particularly strong, with China's UN Ambassador Fu Cong explicitly criticizing Japan and the EU at the United Nations. Ambassador Fu claimed that Japan is "demonstrating military force in the Taiwan Strait and deliberately provoking tensions," sending "extremely erroneous signals" to Taiwanese separatists.

Meanwhile, Japan is accelerating the strengthening of its defense posture domestically. Starting in May, the Japan Maritime Self-Defense Force will digitize the process for bases and vessels nationwide to request supplies such as ammunition and fuel, implementing a system to monitor the storage status of approximately 210,000 items in real-time. This measure aims to enhance sustained combat capability, allowing for seamless resupply to frontline units by instantly grasping the status of ammunition and fuel stockpiles.

Additionally, the Self-Defense Forces conducted military exercises focused for the first time on the southwestern islands near Taiwan. According to reports from Stars and Stripes, this exercise differs from previous training in the southwestern islands, directly addressing a defense scenario for Taiwan. In recent years, Japan has been advancing the buildup of military capabilities along the southwestern island chain, clearly indicating its stance to counter China's increasing military presence around Taiwan and in the East China Sea.

South Korea's positioning is also noteworthy. The Yoon Suk-yeol administration emphasizes building a "stable relationship" with China while maintaining strategic ambiguity regarding the Taiwan Strait issue. This is influenced by China's economic pressure on South Korea during the THAAD deployment in 2017, and South Korea remains cautious about cooperating with U.S. operational plans regarding the Taiwan Strait. However, as U.S.-China tensions deepen, it remains uncertain how long South Korea can maintain this strategic ambiguity.

Australian Foreign Minister Penny Wong also visited Japan, China, and South Korea this week to discuss the impact of the Middle Eastern conflict on energy security. This move indicates that the security issues in Northeast Asia are not merely regional challenges but are interconnected with the risks of the Iran conflict and the blockade of the Strait of Hormuz. As the Iran conflict alters the global deployment patterns of U.S. forces, allies in the Indo-Pacific region face uncertainties regarding the sustainability of U.S. engagement, which is driving the enhancement of defense capabilities in Japan, South Korea, and Taiwan.

In summary, the security situation in Northeast Asia in the spring of 2026 can be described as having entered a structural phase of military tension between Japan and China. The transit through the Taiwan Strait, participation in the Balikatan exercise, and the strengthening of defense in the southwestern islands all indicate that Japan is beginning to position a Taiwan contingency as a concrete security scenario. China is also clearly aware of this and is attempting to prevent Japan's strategic shift by simultaneously escalating diplomatic condemnation and military pressure. This structure of confrontation is unlikely to ease in the short term, and rather, as preparations for the situation in the Taiwan Strait in 2027 intensify, it is highly likely to worsen.