Keen Sword 27 Begins: The Largest-Ever U.S.-Japan Exercise Puts 57,000 Personnel and a New Long-Range Missile to Work

Japan and the United States began the largest version of their Keen Sword joint exercise on Monday morning, putting approximately 57,000 personnel — about 45,000 from Japan's Self-Defense Forces and 12,000 from the U.S. military — through 11 days of drills across Japan, with a particular weight on the southwestern islands that face Taiwan and the East China Sea. Keen Sword 27 runs through October 29 and involves approximately 45 ships and 380 aircraft from the two countries, according to Japan's Joint Operations Command.

It is the first Keen Sword held since Japan established its Joint Operations Command in March of last year, a reform designed to put the ground, maritime and air services under a single operational headquarters — and, in a crisis, to coordinate them with U.S. forces from one room. Gen. Hiroaki Uchikura, chief of Japan's Joint Staff, said at an October 9 press conference that practising troop transportation, resupply, command and control and joint anti-ship operations would improve the allies' ability to deploy forces rapidly and operate together. The exercise programme reflects exactly that list: movement and supply across geographically separated islands, anti-ship combat, missile defence, amphibious operations, cybersecurity, and activities involving space and electromagnetic systems.

A new missile leaves home for the first time

The headline deployment is Japanese. The Type 25 surface-to-ship guided missile — a domestically produced, long-range stand-off weapon with counterstrike capability and a reported range exceeding 1,000 kilometres — was formally deployed to the Ground Self-Defense Force's Camp Kengun in Kumamoto City in March. Keen Sword marks its first tactical deployment outside that home base. Launchers have been transported to the Ohnohara exercise area, spanning parts of Nagasaki and Saga prefectures, where crews will run non-firing drills confirming target-setting procedures and launch preparations. No missiles will be launched; the point is proving the system can move, set up and be aimed as part of a joint operation, with Japanese and U.S. personnel expected to exchange targeting data and jointly practise launch procedures, according to local media reports.

Yomiuri Shimbun has reported that Japan also plans to purchase U.S.-made Tomahawk cruise missiles to strengthen the same counterstrike capability, while noting the practical challenges underneath the announcements: securing sufficient missile inventories and expanding the satellite surveillance networks that long-range targeting depends on. A missile with a 1,000-kilometre reach, on paper, places Chinese coastal areas and North Korea within range. Whether Japan can find, track and coordinate targets at that distance is precisely what an exercise like this is designed to test.

The southwestern islands, and the neighbours watching

The geography is the message. On Yonaguni — Japan's westernmost island, roughly 110 kilometres from Taiwan — the United States will deploy the Navy-Marine Expeditionary Ship Interdiction System, known as NMESIS, while Japan temporarily adds Type 88 anti-ship missiles and Type 03 medium-range air-defence systems. On Ishigaki Island, U.S. HIMARS rocket artillery and NMESIS systems will train alongside Japanese units already stationed there. U.S. Marine Corps Osprey aircraft used Miyako Airport for the first time as the exercise opened, and civilian port facilities are scheduled to be used for equipment-transport training. The U.S. nuclear-powered aircraft carrier USS Theodore Roosevelt arrived at Yokosuka Naval Base on October 16, with the guided-missile cruiser USS Chosin and the destroyer USS Decatur, ahead of the carrier strike group's participation.

On the ground in Okinawa, the exercise was visible from the first morning. Self-Defense Forces Osprey aircraft and transport planes landed at Ishigaki Airport as the drills opened, and training on Ishigaki will include operation of the U.S. military's HIMARS rocket artillery system and the NMESIS surface-to-ship missile system. On Miyako Island, U.S. military Ospreys used Miyako Airport for the first time, and the civilian Hirara Port is scheduled to be used for equipment-transport training. Okinawa Prefecture has asked the Okinawa Defense Bureau to minimise the impact of the training on residents' lives, while the prefectural governor indicated a willingness to accept the use of Ospreys and did not ask that they be kept out of this exercise. That local negotiation, repeated island by island, is part of the exercise too: the southwestern chain is not empty training ground, but home to the communities the posture is meant to defend.

Seven other countries — Australia, Canada, France, Germany, the Netherlands, New Zealand and the Philippines — will also take part in some capacity, though Japan's military did not disclose their personnel numbers or detailed force compositions. The exercise has drawn domestic opposition as well as allied participation: an October 14 protest at Japan's Defense Ministry in Tokyo called for Keen Sword's cancellation, arguing the drills convert the southwestern islands into permanent front-line positions, and Yonaguni's mayor has said the island's capacity has been exceeded. Okinawa Prefecture has asked that the impact of training on residents' daily lives be minimised.

None of that slows the schedule. For the next 11 days, the alliance will practise the unglamorous mechanics — fuel, ferries, runways, radios, targeting data — that determine whether a deterrent posture is real or theatrical. Keen Sword has run, in various forms, for decades. This edition is simply the largest, the first under Japan's new joint command, and the first to put its new long-range missile on the road. The neighbours it is meant to impress are watching; so, increasingly, are the islanders it is staged among.

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