Military Tensions in the Taiwan Strait: Japan Faces the Structural

📡 The Signal — What Happened

Why it matters: China's military pressure around Taiwan has qualitatively changed, forcing Japan, for the first time in the post-war era, to concretize the hypothesis of "a Taiwan contingency equals a Japan contingency" at the policy level. This choice will define the reliability of the Japan-U.S. alliance, regional order, and Japan's security identity itself.

• Military Trends — The Chinese People's Liberation Army (PLA) has gradually expanded the frequency and scale of military exercises around Taiwan since late 2025, with flights across the Taiwan Strait median line becoming routine by early 2026.
• Military Trends — China's aircraft carrier "Fujian" entered service in 2025, dramatically enhancing the deployment capability of its carrier strike group in the waters east of Taiwan.
• Japan's Response — The Ministry of Defense has raised the alert level of Self-Defense Forces units in the Southwestern Islands and strengthened the readiness of missile units on Yonaguni Island and Ishigaki Island.
• Japan's Response — The FY2026 defense budget is projected to reach approximately 8 trillion yen, exceeding 2% of GDP for the first time.
• Japan-U.S. Alliance — At the Japan-U.S. Security Consultative Committee (2+2) in December 2025, a joint statement was issued declaring the stability of the Taiwan Strait as "critically important."
• Japan-U.S. Alliance — The deepening of integrated operational systems between U.S. forces in Japan and the Self-Defense Forces has accelerated, with the frequency of joint command post exercises doubling year-on-year.
• Economic Impact — Amid rising Taiwan contingency risks, Japanese companies are accelerating the diversification of supply chains away from Taiwan. The strategic importance of TSMC's Kumamoto factory, especially for semiconductors, has been re-recognized.
• Diplomacy — Entering 2026, Japan has rapidly strengthened security cooperation with the Philippines and Australia, advancing the construction of a multi-layered deterrence network.
• China's Stance — China maintains its position that "Taiwan unification is a core interest" and has repeatedly warned of military responses to external interference.
• Domestic Politics — Within Japan, public opinion on security policy has become polarized, and discussions on constitutional interpretation regarding the expansion of the scope of collective self-defense have reignited.
• International Environment — Expectations for Japan in the U.S. Indo-Pacific strategy have grown, and it is being asked to play a core partner role in the "integrated deterrence" concept.
• Technological Trends — Japan's development and deployment plan for long-range missiles (stand-off missiles) has been accelerated, with partial operational commencement expected within FY22026.

The current tensions surrounding the Taiwan Strait did not emerge overnight. Their structural roots lie at the intersection of three tectonic shifts: the transformation of the East Asian order after the end of the Cold War, China's rapid rise, and the relative decline of U.S. hegemonic status.

Historically, since the establishment of the People's Republic of China in 1949, the Taiwan issue has remained an "unfinished civil war" for China. During the Taiwan Strait Crises of the 1950s (1954-55, 1958), U.S. military intervention deterred China's armed unification. However, following Nixon's visit to China in 1972 and the normalization of U.S.-China diplomatic relations in 1979, the Taiwan issue has been managed on a delicate diplomatic balance of "strategic ambiguity."

The turning point was the emergence of the Xi Jinping administration in the 2010s. Xi Jinping declared the "great rejuvenation of the Chinese nation" as a national goal and positioned Taiwan's unification as an inseparable element of it. At the 19th Party Congress in 2017, he explicitly stated that "the complete unification of the motherland is an inevitable requirement for the great rejuvenation of the Chinese nation," and at the 20th Party Congress in 2022, he explicitly rejected renouncing the use of force. This hardening of political will, coupled with China's rapid military modernization, has structurally altered the military balance in the Taiwan Strait.

Particularly noteworthy is the dramatic improvement in China's A2/AD (Anti-Access/Area Denial) capabilities. The DF-21D and DF-26 anti-ship ballistic missiles, the YJ-21 hypersonic anti-ship missile, and a rapidly expanding naval force have given China the ability to dramatically increase the cost of U.S. military intervention in a contingency. This fundamentally shakes the traditional premise that "China cannot act if the U.S. military arrives."

For Japan, the Taiwan issue was once a matter that could be treated as "someone else's problem." However, geographical realities no longer permit this. Yonaguni Island is only 110 kilometers from Taiwan. Should a Taiwan contingency occur, the Southwestern Islands would automatically be included in the theater of conflict. During China's military exercises following Pelosi's visit to Taiwan in August 2022, an unprecedented situation occurred where ballistic missiles landed within Japan's EEZ, strongly impressing this geographical reality upon Japanese society.

The three security documents (National Security Strategy, National Defense Strategy, Defense Buildup Program) formulated in December 2022 reflect this shift in perception into policy. The acquisition of counterstrike capabilities, the increase in defense spending to 2% of GDP, and the acceleration of the "Southwestern shift" were all policy changes made with a Taiwan contingency scenario in mind.

However, in 2026, the problem has become even more acute. The "normalization" of China's military pressure is invalidating the traditional dichotomy of "contingency or peacetime." The prolonged gray zone situation forces Japan to maintain a sustained alert posture, depleting the human and material resources of the Self-Defense Forces. Simultaneously, the intensification of strategic competition between the U.S. and China poses a fundamental question to Japan: "To what extent should we align with the U.S.?"

Particularly important is that the shift in Japan's security policy rests on a fragile foundation of domestic political consensus. The increase in defense spending has proceeded via cabinet decisions, without sufficient national debate. There is no clear national consensus on the criteria for exercising counterstrike capabilities, their relationship with collective self-defense, and most fundamentally, the question of "Will Japan fight for Taiwan?"

This structural ambiguity creates a paradoxical situation where it undermines the credibility of deterrence against China and, conversely, increases the risk of escalation. Japan now stands at the greatest security crossroads since the war, and its choices will define the regional order for decades to come.

The delta: The core of the change lies in the military tensions surrounding the Taiwan Strait shifting to a new phase of "normalization of crisis." Previously, military demonstrations were primarily temporary responses to specific events (such as visits by dignitaries to Taiwan), but since late 2025, the Chinese military's presence around Taiwan has transformed into a constantly maintained state. This forces Japan to respond continuously in the gray zone between "contingency" and "peacetime," necessitating a fundamental paradigm shift in its security policy.