<figure id="attachment_465460" class="wp-caption aligncenter" style="width: 2500px;" aria-describedby="caption-attachment-465460"><a href="#" data-ident_hash="f5e271b7"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/04/35a532968c9508d7aedfc8211089ef6d.jpg" alt=""></a><figcaption id="caption-attachment-465460" class="wp-caption-text">“In the latter part of the Pacific War, in 1941, a naval air-defense observation post was placed on Mageshima. Seen from above, the runway was nearing completion.”</figcaption></figure>
<h3>An entire-island U.S.-Japan training facility</h3>
Mageshima Island, part of the Ōsumi Islands in Kagoshima Prefecture.
This small island, measuring approximately 4.5 km north to south and 2.7 km east to west, has been undergoing rapid, around-the-clock construction since 2023.
While there have been cases such as Ishigaki and Miyako Islands where Self-Defense Force bases or garrisons were built on islands, what makes Mageshima significantly different is that the entire island is being turned into a Self-Defense Force base.
The photo above was taken in mid-March this year. From the air, the island’s main 2,450-meter runway and the 1,830-meter crosswind runway—its defining features—are clearly visible. Having runways in different directions allows aircraft to take off and land regardless of weather or wind direction.
Here, training is planned for the Air Self-Defense Force’s latest stealth fighter, the F-35B, including takeoffs and landings, as well as simulated carrier-based aircraft operations conducted by the U.S. Navy, currently based around Iwo Jima. The U.S. Navy aviation units stationed at Iwakuni Air Base in Yamaguchi Prefecture are about 1,400 km from Iwo Jima, but if Mageshima becomes operational, that distance would be reduced to about 400 km, greatly improving mobility.
From above, various piers of different sizes can also be seen. These are designed to allow docking by Maritime Self-Defense Force destroyers and other vessels. Amphibious training areas are also being developed, along with facilities for the Ground Self-Defense Force, making it a true integrated defense complex, with construction progressing steadily.
The number of Self-Defense Force personnel stationed on the island is expected to be between 150 and 200. On the island, living facilities such as barracks, dining halls, baths, recreational facilities, and gyms will be built. However, personnel and their families are expected to live on nearby Tanegashima, about 10 km east of Mageshima.
Official housing is being constructed in the cities and towns of Nishinoomote, Nakatane, and Minamitane on the island, and personnel will commute to Mageshima by boat via Hamasuwaki Port in Nakatane Town. The ferry service will be operated by a private company contracted by the government.
The construction base for the Mageshima project is also located on Tanegashima.
“A worker from the Kanto region said he applied immediately because the pay and conditions were good. People are coming from all over Japan. The only downside is that there’s not much entertainment on Tanegashima.”
A worker originally from Kanto said this while scratching his head, but the nightlife was lively. Restaurants filled with workers from Tokyo, Osaka, and Hokkaido were described by staff as a kind of boom.
New employment opportunities have also been created, and Tanegashima appears to be benefiting economically.
Mageshima also has another important role: serving as a unsinkable aircraft carrier-like fortified island floating in the sea. In the event of conflict, air bases are expected to be primary targets. Fighter jets must land somewhere for fuel and ammunition resupply, but if runways are destroyed, this becomes impossible.
The Ministry of Defense plans to utilize civilian airports as well, a strategy called mobile dispersed operations. Mageshima is located at an appropriate distance from strategic areas such as the Miyako Strait and the Amami Islands, and in the event of a contingency, it is expected to serve as a forward logistics base for aircraft and ships.
Completion is scheduled for 2030. The security environment in Japan’s southwestern region is set to change significantly.
From &#8220;FRIDAY&#8221;, April 17–24, 2026 combined issue.
<figure id="attachment_465461" class="wp-caption aligncenter" style="width: 2500px;" aria-describedby="caption-attachment-465461"><a href="#" data-ident_hash="b0b9d931"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/04/5b4f24a6cefcebff1e0f81f9d3804c26.jpg" alt=""></a><figcaption id="caption-attachment-465461" class="wp-caption-text">“Official housing for personnel is being constructed on Tanegashima. Some facilities in Nakatane Town are already completed and advance personnel have moved in. From there, personnel will commute by boat to Mageshima.”</figcaption></figure>

 Masayuki Kikuchi

 The Magejima Air Base in the Osumi Islands of Kagoshima Prefecture has been under construction day and night at a rapid pace since 2011. It is located at a reasonable distance from the Miyako Strait and the Amami Islands, which China is targeting, and is said to serve as a supply base for fighter aircraft and naval vessels fighting on the front lines in the event of an emergency.

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