2026 Keen Sword: U.S. Marine Corps NMESIS and Japan Ground Self-Defense Force Type 12 Improved Model Conduct Strait Blockade Exercise on Yonaguni Island
Tanaka Takashi2026 Keen Sword: US Marine Corps NMESIS and Japan's Improved Type 12 Conduct Strait Blockade Exercises on Yonaguni Island
In the Japan-US joint integrated exercise "Keen Sword 26," which began on October 19, the US Marine Corps' NMESIS (Naval Mobile Expeditionary Ship Interdiction System) and MADIS (Marine Air Defense Integrated System) were deployed for the first time on Yonaguni Island, approximately 110 kilometers from Taiwan. Unlike traditional exercises that prominently feature aircraft carrier strike groups, this year's focus is on how ground forces dispersed across the southwestern islands can restrict maritime traffic routes.
Two Launchers Deployed on Yonaguni Island
According to Defense News, the range of NMESIS is approximately 115 miles (about 185 kilometers), providing denial capabilities against vessels operating around Taiwan. The ability to operate vehicles as small dispersed units is crucial, emphasizing a character of being "hard to find" as launch points frequently change, rather than relying on a fixed base defense network. MADIS is responsible for protecting these units from small drones and low-altitude threats.
The Japanese side combines the Ground Self-Defense Force's Type 88 anti-ship guided missile, Type 12 anti-ship guided missile, and Type 03 medium-range surface-to-air guided missile (improved version). Notably, the improved Type 12, which has been deployed to the southwestern islands since the end of March and is referred to in the exercise as the "Type 25 anti-ship guided missile," is reported to have a range of approximately 1,000 kilometers. While the US military's NMESIS is tasked with localized coastal denial, Japan's long-range missiles are configured to threaten broader approaches by utilizing the depth of the island chain.
Absence of Aircraft Carriers Indicates a Practical Shift
This year's Keen Sword involves approximately 45,000 Japanese Self-Defense Force personnel and units from nine countries. Meanwhile, the aircraft carrier "George Washington," which has been a symbolic presence in the past, is not participating, as US carriers are assigned to missions in the Middle East. This absence may appear to be a weakness, but the author believes it is evidence that Japan and the US are shifting from a concept of "waiting for the fleet to arrive" to one of segmenting maritime areas with sensors and missiles pre-positioned on islands.
Cross-referencing the framework of the exercise published by the Ministry of Defense with media reports, the core of this exercise is not the missile range itself, but whether the US and Japan can connect launch command, target information, resupply, and post-damage redeployment. The radar on Yonaguni Island was installed in 2016, but the island's port, roads, and air routes are not exclusively for military transport. Even transporting large equipment from Kubura Port can create friction with local residents. In other words, the sustainability of dispersed operations is more dependent on the capacity of civilian infrastructure than on the performance of the launchers.
The Vulnerability of SLOC Behind Deterrence
Placing NMESIS and the long-range improved Type 12 on Yonaguni Island in an area where Chinese Coast Guard vessels are active is a clear signal of intent regarding a Taiwan contingency. However, missile units require ammunition, fuel, communications, and maintenance personnel. If the Chinese side attacks runways, ports, and communication nodes, even if the launchers remain unscathed, the units will become isolated. Additionally, if fishing and transport activities around Yonaguni Island are restricted, the maritime traffic routes during peacetime will bear the costs of deterrence.
Ultimately, the new reality of the Japan-US alliance demonstrated by Keen Sword 26 is not a competition of the number of vessels, but rather a war of attrition regarding how long launchers can be sustained moving from island to island. Japan's next challenge is not to promote a range of 1,000 kilometers. It is whether it can establish a system and supply network that allows for monitoring SLOC while protecting residents and resupplying even after communication disruptions and port closures.
Main Sources
The U.S. Marine Corps deployed NMESIS and MADIS on Yonaguni Island during the Keen Sword 26 exercise, which began on October 19, 2026. Approximately 45,000 Japanese Self-Defense Forces personnel participated, focusing on maritime traffic control and missile deployment. The exercise marks a strategic shift towards utilizing island-based systems for regional deterrence.
- The U.S. Marine Corps deployed NMESIS and MADIS for the first time on Yonaguni Island during Keen Sword 26.
- The exercise began on October 19, 2026, with approximately 45,000 Japanese personnel involved.
- The NMESIS has a range of about 115 miles, capable of denying access to vessels near Taiwan.
- Japan's Type 12 missile system has a reported range of approximately 1,000 kilometers.
- The absence of U.S. aircraft carriers indicates a shift in military strategy towards island-based operations.