The US military is preparing to deploy its NMESIS anti-ship missile system to Yonaguni, Japan’s westernmost inhabited island and the Japanese territory closest to Taiwan, during a major joint exercise later this month.
The move will put the mobile coastal weapon closer to Taiwan than during its previous deployment in Japan and comes as Washington and Tokyo expand their ability to operate in the islands stretching toward the Taiwan Strait.
The deployment is part of Keen Sword, the biennial US-Japan exercise scheduled for October 19-29. NMESIS will operate alongside Japanese and US forces at Yonaguni, while the exercise will also introduce the US Marine Corps’ MADIS short-range air-defense system to the island.
NMESIS moves closer to Taiwan
Yonaguni sits roughly 62 miles, east of Taiwan. That makes it significantly closer to Taiwan than Ishigaki, where US Marines deployed NMESIS during the Resolute Dragon exercise in 2025, when it was about 150 miles from Taiwan, the South China Morning Post reported.
The Navy-Marine Expeditionary Ship Interdiction System, or NMESIS, is a ground-based anti-ship weapon designed for mobile operations in coastal and island environments. The Marine Corps describes it as a highly mobile and rapidly deployable system intended for sea denial and littoral protection.
The system uses a remotely operated launcher mounted on an unmanned vehicle and carries Naval Strike Missiles capable of engaging ships at ranges beyond 115 miles. That range gives a launcher positioned on Yonaguni the ability to threaten ships operating across a substantial area around the island and toward Taiwan.
The US has already demonstrated the concept elsewhere in the region, with the NMESIS deployed to the Philippines’ Batanes Islands during Balikatan exercises, another location close to Taiwan, and to Ishigaki during last year’s Japan-US drills.
The island becoms a military node
Keen Sword will also establish a joint coordination center at the Yonaguni garrison, where Japanese and US forces will conduct island-defense exercises and coordinate with equipment deployed at other locations. The exercise is intended to improve how the two militaries operate across Japan’s southwestern island chain.
The US Marines will also deploy MADIS to Yonaguni for the first time. The system is designed to provide short-range protection against drones, helicopters and low-flying aircraft, adding an air-defense layer alongside NMESIS’ anti-ship capability. The Marine Corps’ 12th Marine Littoral Regiment formally received both systems in June.
Furthermore, Japan has also been strengthening its own military presence on Yonaguni. The island has hosted a Ground Self-Defense Force garrison since 2016, while Tokyo has plans to add additional air-defense capabilities in the coming years.
Such developments makes Yonaguni increasingly relevant to the broader concept of distributed forces across the first island chain, which stretches from Japan through Taiwan and the Philippines. The US 2026 National Defense Strategy explicitly calls for strengthening a denial defense along the First Island Chain and working more closely with regional allies.