Yonaguni Island, Japan’s westernmost inhabited island, lies about 110km from Taiwan. During this month’s Keen Sword exercise, the US will deploy its Navy-Marine Expeditionary Ship Interdiction System, known as NMESIS, there for the first time.
The joint exercise is scheduled to run from 19 to 29 October. Japan’s Ground Self-Defense Force also plans to deploy surface-to-ship missiles with a range of several hundred kilometers on Yonaguni for the first time during an exercise.
Japan’s Self-Defence Forces and the US military will also establish a joint coordination centre on the island.
NMESIS is a ground-based, uncrewed US Marine Corps missile platform intended for sea denial and protection close to shore. It carries two Naval Strike Missiles and has a range of more than 185km.
Each launcher is mounted on an unmanned, remotely driven version of Oshkosh Defense’s Joint Light Tactical Vehicle, called ROGUE-Fires. The launcher is designed to move between islands and conceal itself.
The 3rd Marine Littoral Regiment received the first NMESIS launchers in November 2024. The system arrived in Japan in July 2025.
It was stationed on Okinawa’s Ishigaki Island during the Resolute Dragon drills in September last year. Ishigaki is roughly 127km east of Yonaguni and about 240km from Taiwan. NMESIS will return to Ishigaki during Keen Sword.
The drills involve 45,000 Japanese and US troops, 40 vessels and 370 aircraft, with some forces from Australia and Canada also taking part. Tilt-rotor Ospreys will fly to Yonaguni for the first time.
Keen Sword takes place across Japan, including at the two countries’ military bases through 1 November. An SDF spokesman told AFP that the Yonaguni drill would practise bringing out residents and tourists during a natural disaster.
Admiral Steve Koehler, commander of the US Pacific Fleet, told reporters on Tuesday: 'Keen Sword will ensure we maintain our advantage over those who seek to undermine the rule-based international order.'
Prime Minister Sanae Takaichi has said that a military attack on Taiwan or a naval blockade by Beijing could constitute a ‘survival-threatening situation’ for Japan and justify a military response.
In August, a Chinese military aircraft made the first confirmed incursion by China into Japanese airspace.
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