Photo/Illutration The Ground Self-Defense Force's 1st Airborne Brigade takes part in the Keen Sword joint military exercise. (Provided by SDF Joint Staff)

The largest joint Japan-U.S. military exercise may have provided the eavesdropping Chinese military with a wealth of intelligence.

A total of 45,000 members of the Self-Defense Forces and U.S. military participated in the Keen Sword joint military exercises, which began on Oct. 23 and will conclude on Nov. 1.

A primary aim of the drills was a simulated response to a military encounter off Taiwan.

Keen Sword was mainly held in the Nansei chain of islands extending from south of Kyushu and covering Okinawa Prefecture. Among the training conducted was evacuating residents and injured troops from those islands to the main islands of Okinawa or Honshu.

Keen Sword has been held since 1986 at about two-year intervals. This year’s exercise was held on the assumption that the SDF’s joint operations command to be established in spring 2025 was already in place. The new command will integrate operations of the three SDF branches.

A total of 33,000 SDF members participated and 30 ships and 250 aircraft were used. From the U.S. military, a total of 12,000 members took part. The Australian and Canadian militaries also took part in some of the exercises.

At his Oct. 25 news conference, Defense Minister Gen Nakatani said, “I am confident that displaying the strong will and cooperation between Japan and the United States will lead to securing not only our defense but the peace and stability of this region.”

But the larger scale of the joint military exercise means more opportunity for enemy forces to acquire intelligence. For example, the radio communications between units involved during Keen Sword can be intercepted and analyzed for future reference.

Defense Ministry officials believe the recent incursions into Japanese airspace by Chinese and Russian military intelligence aircraft were attempts to gather radio communications between SDF units.

A Chinese Y-9 intelligence-gathering aircraft was spotted on Oct. 28 flying over several of the islands of the Okinawa chain before returning in the direction of China. Two other Chinese aircraft were also spotted flying above an area where Keen Sword exercises were being conducted.

Air SDF fighter jets were scrambled to trail the three Chinese aircraft.

(This article was written by Mizuki Sato and Nobuhiko Tajima.)

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