Japan urges defense of first island chain and maintenance of U.S. security commitments amid China’s military expansion
China-Japan tensions intensify after remarks on a Taiwan contingency, with diplomatic and trade clashes extending to military confrontations
Japan strengthens long-range strike capabilities with U.S. support; China criticizes “neo-militarism”

Security tensions between Japan and China are escalating. Since Japan’s remarks on the Taiwan Strait last year triggered a diplomatic dispute between the two countries, clashes have spread to maritime affairs and trade, while military confrontations have also intensified. China has strongly objected, characterizing Japan’s defense buildup as a move toward “neo-militarism.” Japan, meanwhile, is further strengthening security cooperation with the United States, wary of China’s expanding military power and its potential advance into the first island chain.

Japan Highlights Wariness of China

According to a Nikkei Asia report on the 25th (all dates hereafter are local time), Yoshihide Yoshida, former chief of staff of Japan’s Self-Defense Forces Joint Staff, outlined “three red lines” that the United States and its allies must uphold to counter China’s military expansion at the 13th Mount Fuji Dialogue, a U.S.-Japan policy forum held in Tokyo on the 24th. These were defending the first island chain linking Okinawa, Taiwan and the Philippines; maintaining U.S. nuclear deterrence; and securing Western superiority in advanced technologies such as artificial intelligence (AI) and quantum technology. He noted that China is rapidly catching up with the United States in military power and advanced technology, and has already pulled ahead in some areas. He also stressed the importance of defending the first island chain through sustained U.S. military engagement. Citing the so-called “Acheson Line,” under which U.S. Secretary of State Dean Acheson excluded the Korean Peninsula and Taiwan from the Far Eastern defense perimeter in 1950, he emphasized that Washington must maintain clear defense commitments in the region.

Japanese participants also focused on how changes in U.S.-China relations could affect East Asia’s security order. With U.S. President Donald Trump and Chinese President Xi Jinping holding three meetings over the past year in an effort to improve relations, concerns are growing that Japan could be sidelined. Masataka Okano, former secretary general of Japan’s National Security Secretariat, said, “The status quo in East Asia is changing gradually and covertly, out of public view,” adding, “We must pay attention to China’s incremental expansion of influence.” Regarding the U.S.-Japan alliance, he said, “It is time to consider not merely the alliance’s strength, but how to enhance its sustainability,” arguing that “a security vacuum must not emerge in Asia.”

China-Japan Rift Deepens

Japanese officials’ efforts to counter China are seen as stemming from the diplomatic and security dispute between the two countries that intensified in November last year. The immediate trigger was a statement by Japanese Prime Minister Sanae Takaichi at a House of Representatives Budget Committee meeting on November 7 last year. Takaichi said that if China used warships to employ force against Taiwan, it could constitute a “survival-threatening situation” under Japan’s security legislation, allowing the exercise of collective self-defense. China strongly objected, accusing Japan of seeking military intervention in the Taiwan issue. That same month, Chinese Consul General in Osaka Xue Jian posted threatening remarks directed at Takaichi on social media. China’s Foreign Ministry subsequently formally demanded that she retract her statement and warned that Japan would have to bear responsibility for all consequences. The Japanese government, however, refused to retract the remarks, saying they did not go beyond the scope of existing security policy, and the two countries summoned each other’s ambassadors to lodge protests.

The dispute soon spread to economic and people-to-people exchanges, as well as maritime security. On November 14 last year, the Chinese government advised its citizens to refrain from visiting Japan. A trilateral culture ministers’ meeting involving South Korea, China and Japan, scheduled for the 24th of that month, was also postponed at China’s request. Around the same time, four China Coast Guard vessels entered territorial waters around the Senkaku Islands, which Japan effectively controls and China calls Diaoyu Dao. On December 6 last year, a J-15 fighter from the Chinese aircraft carrier Liaoning directed its radar at a Japan Air Self-Defense Force F-15 fighter over international waters near Okinawa. Japan’s Defense Ministry described the incident as a dangerous act threatening aircraft safety and protested to China, but Beijing countered that Japanese fighters had interfered with its navy’s normal training activities.

Military Tensions Between the Two Countries Intensify

This year, the confrontation has extended to trade restrictions and maritime enforcement. In January, China’s Ministry of Commerce announced a ban on exports to Japan of dual-use goods that could contribute to strengthening Japan’s military capabilities. The restrictions included certain rare-earth-related items used in semiconductors, electric vehicles and defense industries. In February, Japan’s Fisheries Agency seized a Chinese fishing vessel and arrested its captain after the vessel failed to obey an order to stop in Japan’s exclusive economic zone (EEZ) near Nagasaki Prefecture. It was Japan’s first seizure of a Chinese fishing vessel since 2022. At the time, China’s Foreign Ministry urged Japan to ensure the safety and legitimate rights and interests of the Chinese crew.

Japan is also stepping up efforts to strengthen its long-range strike capabilities in response to China’s expanding military influence. According to Kyodo News, Japan’s Defense Ministry operationally deployed domestically produced long-range missiles for the first time in March at Camp Kengun in Kumamoto Prefecture, Kyushu, and Camp Fuji in Shizuoka Prefecture. This was the first instance of Japan turning the “counterstrike capabilities” specified in its revised 2022 National Security Strategy into an operational capability. Specifically, Camp Kengun received Type 25 surface-to-ship guided missiles, an upgraded version of the existing Type 12 surface-to-ship guided missile, with a range of approximately 1,000 kilometers. Launched from Kyushu, the weapon can strike China’s coast and waters around Taiwan. Camp Fuji reportedly received Type 25 hypervelocity gliding projectiles, which fly along irregular trajectories that make them difficult to intercept.

Table 1. Key Developments in the China-Japan Dispute

China Strongly Objects to “Revival of Neo-Militarism”

The Chinese government strongly objected to Japan’s moves, warning against a revival of “neo-militarism.” At a regular briefing in April, Chinese Foreign Ministry spokesperson Mao Ning said, “Japan’s deployment of offensive weapons under the pretext of defense and counterstrikes goes far beyond the principles of self-defense and an exclusively defense-oriented policy.” She criticized the move as “violating documents with international legal force, including the Cairo Declaration, the Potsdam Declaration and Japan’s Instrument of Surrender, as well as Japan’s Constitution and established norms.” She added, “This reflects a shift by Japan’s right-wing forces toward an aggressive and expansionist security policy,” arguing that “Japan’s neo-militarism threatens regional peace and stability, and the international community must remain highly vigilant.”

At the same briefing, she also cited an incident in which an active-duty Japanese Self-Defense Forces officer trespassed into the Chinese Embassy in Japan. In March, Second Lieutenant Kodai Murata of the Japan Ground Self-Defense Force climbed over the wall of the Chinese Embassy in Tokyo while carrying a bladed weapon and was arrested by police for trespassing. Mao said, “Rather than reflecting on its inadequate management of the Self-Defense Forces, Japan is stoking fears of external threats and accelerating its military buildup,” calling this “a very dangerous trend.” She urged Japan to “deeply reflect on its history of militarist aggression, honor its commitments in military and security affairs, and act prudently.”

Structural Changes in U.S.-Japan Military Cooperation

Active U.S. support is a key reason China is closely watching Japan’s efforts to strengthen its military capabilities. Under Article 9 of its pacifist Constitution, which took effect in 1947 after its defeat in World War II, Japan renounced war and the use of force to settle international disputes and has faced constitutional restrictions on maintaining military forces. Although it established the Self-Defense Forces in 1954 with U.S. support, its use of military power centered on the principle of an exclusively defense-oriented policy aimed at defending against armed attacks on Japan itself. In recent years, however, China’s military buildup and intensifying tensions in the Taiwan Strait have prompted Japan to strengthen its defense capabilities, a direction the United States has also supported. At the U.S.-Japan summit in April 2024, then-U.S. President Joe Biden endorsed Japan’s plans to acquire counterstrike capabilities and increase defense spending. At the two countries’ foreign and defense ministers’ meeting in July that year, officials also discussed ways to expand bilateral cooperation on the operation of Japan’s counterstrike capabilities. At the summit between President Trump and then-Japanese Prime Minister Shigeru Ishiba in February last year, the United States reaffirmed that it “welcomes Japan’s policy of strengthening its defense capabilities.”

More recently, the two countries have also been strengthening their combined operational capabilities as the United States actively uses military positions on Japan’s southwestern islands to deter China’s advance into the western Pacific. During the large-scale joint exercise Keen Sword 27, being held from the 19th to the 29th of this month, the United States and Japan plan to deploy mobile missile systems to Japan’s Yonaguni Island, near Taiwan. The U.S. Marine Corps will deploy the Navy/Marine Expeditionary Ship Interdiction System (NMESIS) and the Marine Air Defense Integrated System (MADIS) there. Japan’s Self-Defense Forces will also deploy long-range missile units to participate in island defense and maritime access denial drills. Rather than concentrating large numbers of troops at a single base, the plan is to disperse small units equipped with anti-ship and air-defense missiles across key positions along the first island chain to counter the Chinese military’s maritime advance.