Faced with China’s rapid military rise, security tensions are growing in Japan, especially in the Nansei Islands, the southwestern chain that includes Okinawa.

The seriousness of the situation can be understood from the joint statement issued after the Japan-U.S. summit held on February 7 between Japanese Prime Minister Ishiba Shigeru and U.S. President Donald Trump. For the first time the statement cited the “increasing bilateral presence in Japan’s Southwest Islands” as one of the efforts to strengthen the alliance.

In the middle of February, as part of a press tour organized by the Foreign Press Center Japan, I visited three key military locations in the Nansei Islands: the Japan Air Self-Defense Force (JASDF)’s Naha Air Base, the Japan Maritime Self-Defense Force (JMSDF)’s Naha Air Base, and Yonaguni Island, the nation’s westernmost “border island.”

The “Air Fortress” in the Nansei Islands Region

The JASDF’s Naha Air Base is Japan’s “air fortress” in the Nansei Islands region, which spans about 1,200 kilometers from the Osumi archipelago off Kagoshima Prefecture – at the southern tip of Kyushu, the most southwestern of Japan’s four main islands – to Yonaguni near the Taiwanese coast. This length is comparable to that of Honshu, the largest of Japan’s four main islands.  

In 2017, the Japanese Ministry of Defense upgraded the Southwestern Composite Air Division at the Naha Air Base to the Southwest Air Defense Force (SWADF) to strengthen the air defense system in the south of Japan.

Including the SWADF, the JASDF has four Air Defense Forces: the Northern Air Defense Force (headquartered at Misawa Air Base), the Central Air Defense Force (headquartered at Iruma Air Base), and the Western Air Defense Force (headquartered at Kasuga Air Base).

What is surprising is the size of the airspace that the SWADF is responsible for. It covers a vast expanse of skies that stretches about 920 kilometers east-to-west and 780 kilometers north-to-south.

A map showing the coverage area of the Southwest Air Defense Force. Map from the JASDF.

As China’s military activities around the Nansei Islands have become more intense, the mission of the Naha Air Base of the JASDF has become more challenging.

In response to foreign military aircraft approaching the country’s airspace, the SWADF scrambled aircraft some 401 times in fiscal year 2023, accounting for 60 percent of the total number of scrambles by the four Air Defense Forces nationwide. Since fiscal year 2013, when China established an Air Defense Identification Zone over the disputed Senkaku/Diaoyu Islands in the East China Sea, the number of scrambles has exceeded 400 every year.

However, SWADF points out that the Chinese military posture cannot be measured by the number of scrambles alone. This is because the quality of their activities has changed in recent years, with the operational area of ​​Chinese military aircraft expanding and the People’s Liberation Army Navy (PLAN)’s aircraft carrier strike group passing through the straits of the Nansei Islands and operating regularly in the Pacific Ocean.

Specifically, Chinese military aircraft, which had operated over the East China Sea before 2012, have flown over the Miyako Strait and advanced into the Pacific Ocean since 2013. In addition, since 2015, they have also been operating over the Tsushima Strait and........

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