The US Marine Corps plans to send anti-ship and air-defence missile systems to Japan’s Yonaguni Island for the first time during the Keen Sword exercise, scheduled for 19–29 October 2026. The deployment will put the systems on Japan’s westernmost inhabited island, approximately 110 kilometers from Taiwan and near sea routes linking the East China Sea with the Pacific.
The exercise will bring together Japan’s Self-Defense Forces, the US military and troops from nine countries, including Australia and France. Approximately 45,000 Japanese Self-Defense Forces personnel are due to take part.
The Marine systems are the Navy-Marine Expeditionary Ship Interdiction System, known as NMESIS, and the Marine Air Defense Integrated System, or MADIS. NMESIS combines an unmanned ground vehicle with a launcher carrying two Naval Strike Missiles. The missiles have a publicly reported range of approximately 185 kilometers, potentially bringing waters off northeastern Taiwan within reach.
MADIS is intended for short-range air defence. Its vehicle-mounted sensors and weapons are designed to counter drones, helicopters and low-flying aircraft.
The Naval Strike Missiles were developed by the Norwegian company Kongsberg. They travel at subsonic speed close to the water’s surface.
The systems arrived with the Okinawa-based 12th Marine Littoral Regiment, 3rd Marine Division in June 2026. Yonaguni’s local government disclosed the planned deployment on Friday, 4 October 2026, after the Okinawa Defense Bureau relayed the plans on 1 October 2026.
The exercise will also involve other missile assets nearby. The US Army will deploy High Mobility Artillery Rocket Systems, known as HIMARS, to Camp Ishigaki, approximately 80 miles from Yonaguni, while the Army’s Typhon missile launcher is to move to Okinawa mid-month.
Japanese and US forces will establish a joint coordination centre on Yonaguni and hold tabletop drills on island defence. According to Stars and Stripes, a spokesperson for the Joint Staff Office stated that none of the systems would be fired during Keen Sword.
Yonaguni has already become part of Japan’s surveillance posture. Japan established radar and surveillance facilities there in 2016. During Chinese exercises around Taiwan in August 2022, a Chinese ballistic missile landed in waters approximately 80 kilometers from the island.
The deployment reflects the Marine Corps’ Force Design modernisation programme, which moves away from heavy equipment such as tanks in favour of mobile expeditionary units, precision missiles, drones and reconnaissance capabilities for contested coastal areas. Defense analyst Harrison Kass called the planned deployment part of a “significant transformation in Marine Corps strategy.”
Keen Sword 27 will be the 18th edition of an exercise that began in FY1985. Japanese Self-Defense Forces participation has risen from approximately 26,000 personnel in 2022 and 33,000 in 2024 to approximately 45,000 in 2026.
The deployment comes as ties between Beijing and Tokyo remain at their lowest point in decades following remarks by Japanese Prime Minister Sanae Takaichi about Taiwan. In November 2025, China’s Ministry of Foreign Affairs described Japan’s plan to deploy Type 03 medium-range surface-to-air guided missiles to Yonaguni as extremely dangerous.
Comments (0)