MANILA, Philippines — The U.S. Marine Corps will deploy its ground-based anti-ship and air-defense systems to Japan’s southwesternmost island for exercise Keen Sword, placing new U.S.-Japan capabilities on an island sitting just 110 kilometers from Taiwan.
Keen Sword, the largest U.S.-Japan biennial joint drill, will feature two key systems of the Marine Corps’ littoral force: the anti-ship NMESIS (Navy-Marine Expeditionary Ship Interdiction System) and air-defense MADIS (Marine Air Defense Integrated System).
Yonaguni’s local government disclosed the deployment on Friday, a day after the Okinawa Defense Bureau relayed deployment plans on Oct. 1.
The systems will be deployed to Yonaguni for the first time, as this year’s iteration shifts to ground-based, multi-island, sea-denial operations aimed at distributing American and Japanese forces across the southwestern islands.
The deployment also reflects a broader shift by the United States and Japan toward mobile missile and air-defense systems that can operate from scattered islands.
NMESIS and MADIS form the cornerstone of the U.S. Marine Corps’ force design modernization and restructuring plan, which moves away from heavy armored platforms to focus on small-unit, expeditionary forces that can capture and defend islands.
NMESIS can strike targets at around 115 miles and could threaten ships operating in waters around Taiwan. The reported deployment, in turn, has drawn criticism from Chinese military experts even while China’s PLA Navy and coast guard vessels have increased activities around Taiwan.
The NMESIS and MADIS systems first arrived with the Okinawa-based 12th Marine Littoral Regiment 3rd Marine Division in June. The units were earlier deployed to the Philippines’ northern Batanes Islands and western Laoag province during the Balikatan drills.
The deployment comes as Japan tests what defense officials describe as standoff-strike capabilities, missile systems that can strike targets far from enemy weapons, while strengthening its southwestern islands for distributed military operations.
According to the Ministry of Defense, troops from nine countries, including the Australian and French armies, will join 45,000 Japanese Self-Defense Forces personnel for this year’s exercise, which will run from Oct. 19 to 29.
The exercise will also bring together a number of U.S. and Japanese ground-based missile systems.
The U.S. Army will deploy HIMARS (High Mobility Artillery Rocket Systems) weapons to Camp Ishigaki, some 80 miles from Yonaguni.
The Army’s Typhon missile launcher will also be moved to Okinawa mid-month, although no disclosures have been made about whether the mid-range system will be used for the exercise.
In past iterations of the drill, the USS George Washington joined the exercises, but the carrier strike group was sent to the Arabian Sea in August to replace the USS Abraham Lincoln, which was returning home after a prolonged deployment.
That prominent naval absence is expected to emphasize the exercise scenario shift toward a land-based network of mobile systems.
Last year, exercises in Yonaguni focused on maximizing the island as a forward operating base. This year, Keen Sword will showcase the Ground Self-Defense Force’s three anti-ship missile systems, which are the core of Japan’s long-range standoff-strike capabilities.
The JGSDF will train with the new ground-launched Type-25 surface-to-ship guided missile system, formerly known as the upgraded Type-12, which was fielded across the Nansei Islands in late March. The Type-25 SSM has a strike reach of 1,000 kilometers.
The lineup also includes the Type-88 ground-to-ship missile and the upgraded Type 03 Chu-SAM Kai medium-range ground-to-air guided missile.
Keen Sword was originally planned as a much larger exercise, local government officials said, but opposition forced the ministry to scale it down to its current iteration.
Yonaguni is Japan’s last inhabited island in the Nansei, a chain of scattered islands in southwestern Okinawa and a fast-emerging flashpoint amid rising tensions around Taiwan.
The JGSDF set up a radar and surveillance system on the island in 2016 to fill a “surveillance vacuum” in the seascapes stretching from the island to Taiwan, according to officials.
The island has seen increased joint exercises between Japanese and U.S. troops while it faces incursions from Chinese ships.
In June this year, the government reported incursions by Chinese Coast Guard ships encroaching on Japan’s exclusive economic zone between Yonaguni and Taiwan. In 2022, China’s ballistic missile landed just 80 kilometers from the island.
While tensions surround the island, local officials have raised concerns about the use of civilian roads, ports, and airways.
Large equipment for the exercise will be transported by sea through Kubura Port, and local authorities have asked residents to avoid using roads during the movement of military equipment.
There are also concerns after a Japan Self-Defense Forces V-22 Osprey was involved in a ground-strike incident in the same exercise in 2024. The incident prompted then-defense minister Gen Nakatani to order the grounding of Japan’s 17 Osprey aircraft.
This year, however, the V-22 Osprey will not participate, Yonaguni Mayor Tsuneo Uechi told Mainichi Shimbun on Oct. 2.
While the island understands the need for military training, Uechi said it is not ready for large-scale exercises that exceed the island’s capacity. The local government remains opposed to the exercises and continues to hold talks with the defense ministry.
Leilani Chavez is an Asia correspondent for Defense News. Her reporting expertise is in East Asian politics, development projects, environmental issues and security.
