Japan is accelerating the construction of a military training base on Mageshima Island for US and Japanese F-35 fighter jets as it steps up efforts to counter the growing threat from China. The base, purchased for $146 million in 2019, is now slated for completion in March 2030—three years behind schedule but with construction progressing rapidly.

The Base

The Japanese government purchased Mageshima, an uninhabited islet in Kagoshima prefecture, in 2019. By the end of the decade, it is to serve as the main flight operations training center for F-35Bs—the short takeoff and vertical landing variant of the Lockheed Martin stealth jet flown by the US Marine Corps and its Japanese counterpart.

Construction began in January 2023 and has continued rapidly since then. The base completion is now expected in March 2030, delayed from the original 2027 target due to manpower and material shortages, rough sea conditions, and unsuitable local earth for landfill work.

At present, major military facilities—including a 2,000-meter runway, ammunition depots, fuel infrastructure such as storage tanks, and a temporary pier capable of accommodating large warships—have already taken shape, according to Chinese state media reports citing unnamed analysts.

The number of workers involved in construction, now in its third year, surpassed 6,000 in October for the first time—1,000 more than in December 2024. The base will station between 150 and 200 Japan Self-Defense Forces personnel.

Strategic Location

Mageshima is located in the narrow Osumi Strait, one of the few waterways used by the Chinese navy to gain access to the Philippine Sea and the wider Pacific Ocean. This positioning makes it a critical chokepoint for monitoring Chinese naval movements.

The island sits approximately 400 kilometers south of the US Marine Corps Air Station Iwakuni in Yamaguchi Prefecture, where US F-35Bs are currently based. The new facility will provide a much more accessible training location than the current site at Iwoto Island, which is 1,250 kilometers south of Tokyo.

Chief Cabinet Secretary Hirokazu Matsuno emphasized the base’s importance, stating it is “indispensable” for US aircraft carriers to operate constantly in the Asia-Pacific region.

Japan’s F-35 Fleet Expansion

Japan is planning significant expansion of its F-35 capabilities in the coming years. The country is set to field a second F-35B squadron by 2030, according to a Japan Ministry of Defense document.

The base will enable field carrier landing practice for the US Navy once or twice a year, while the Japan Self-Defense Forces will use it to practice takeoffs and landings with its future shipborne F-35B Lightning II Joint Strike Fighters, as well as to carry out drills with its MV-22B Osprey tiltrotor aircraft.

The base will have two runways—approximately 2,450 meters and 1,830 meters long—along with a fuel facility, ammunition storage, a hangar, and several ports. The runways are expected to be completed in late 2027, possibly allowing the US military to start exercises at the new site before the rest of the base is finished.

Broader Military Buildup

The Mageshima base is just one node in a years-long effort by Japan to bolster its military presence in its far-west islands, including those closest to China-claimed Taiwan.

Last month, Japanese Defense Minister Shinjiro Koizumi confirmed plans to deploy anti-air missiles on Yonaguni, a Ryukyu islet just 60 miles from Taiwan’s east coast. Beijing condemned the move as “extremely dangerous,” saying it would further escalate military rivalry.

The Japan Self-Defense Forces established a garrison on Ishigaki Island in the southwest as early as 2023, deploying Type 12 ground-launched anti-ship missiles and Type 03 medium-range surface-to-air missiles.

China’s Response

The work has not gone unnoticed in Beijing. Chinese state broadcaster CCTV released a special report highlighting the pace of Japan’s rearmament campaign, aired amid an ongoing diplomatic spat between the two governments.

A report published by the Chinese state-run tabloid Global Times said the construction on Mageshima had “accelerated markedly.” The newspaper obtained exclusive satellite images showing the rapid pace of military construction on the island.

Song Zhongping, a Chinese military affairs expert, told the Global Times that the base could serve not only as a training facility for pilots but also as part of Japan’s preparations for “military expansion.” He also observed Mageshima’s strategic proximity to the Ryukyu Islands.

Chinese Foreign Ministry spokesperson Mao Ning said during a November 21 press conference: “In recent years, Japan has kept easing the restrictions and seeking military buildup. If Japan seeks to go back to the path of militarism, violate its commitment to peaceful development and disrupt the postwar international order, the Chinese people will not allow it, and the international community will not allow it.”

Escalating Tensions

These developments come amid heightened tensions between Tokyo and Beijing following Prime Minister Sanae Takaichi’s November 7 remarks that Japanese forces could intervene in the Taiwan Strait to help US forces break a potential Chinese blockade of the island during a crisis.

Takaichi intimated a military blockade would present a “survival-threatening situation” for Japan, a rare justification for military action under the country’s pacifist postwar constitution. While previous Japanese leaders had linked the situation around Taiwan to Japanese security, Takaichi’s was the most explicit articulation yet of conditions for a possible intervention.

Chinese officials and state-linked commentators have launched a sustained campaign of condemnation, demanding that she retract the statement and accusing Japan of reviving the militaristic adventurism of the 1930s and 1940s.

The tensions have already manifested in dangerous military encounters. In December 2025, Chinese J-15 carrier-based fighters locked fire-control radar onto Japanese F-15 jets in two separate incidents near Okinawa, prompting Japan to summon China’s ambassador in protest.

Japan’s Strategic Rationale

Japan’s Defense Ministry previously said of the Mageshima base: “It will hold great significance for Japan’s peace and security. In the event of a large-scale disaster, rescue operations in the region could also be conducted more effectively.”

United States defense planners view Japan, a US treaty ally, as strategically vital to its military posture on the front lines of the Western Pacific. China’s People’s Liberation Army is pushing up against the First Island Chain, a string of islands the Pentagon views as key to containing its East Asian rival in the event of a conflict.

Tokyo has vowed to ramp up defense spending to grow its role in the US-led defense network, and the work at Mageshima is part of Japan’s largest military buildup in four decades.

What Happens Next

The Mageshima base is slated for completion in March 2030, with the runways expected to be finished in late 2027. With more than 6,000 workers now on site and major facilities already taking shape, the base represents a significant expansion of US-Japan military cooperation and a clear signal to Beijing about allied resolve in the Western Pacific.

We’ll continue to monitor the construction progress and regional tensions as this strategic facility nears completion.