The Japan Ground Self-Defense Force Type-25 Anti-Ship Missile and the U.S. Marine Corps NMESIS Demonstrate a Shift in Southwest Defense During Exercises Around the Senkaku Islands in 2026

From October 19 to 29, the Japan-U.S. joint integrated exercise "Keen Sword 27" will see the deployment of the U.S. Marine Corps' NMESIS (Naval Mobile Expeditionary Security System) and MADIS (Mobile Air Defense Integrated System) for the first time on Yonaguni Island. Positioning mobile anti-ship and air defense capabilities approximately 110 kilometers from Taiwan is not merely an addition to training items; it represents a shift from the concept of defending the southwestern islands as a single base to operating them as a dispersed firing network across multiple islands.

Three Firing Systems Gather on Yonaguni Island

According to the Ministry of Defense, approximately 45,000 personnel from the Self-Defense Forces and units from nine countries will participate in this exercise. The Japan Ground Self-Defense Force will combine the Type-25 surface-to-ship guided missile, which has been deployed to the southwestern islands since the end of March, with the conventional 88-type surface-to-ship missile and the improved Type-03 medium-range surface-to-air guided missile. The Type-25, an upgraded version of the old Type-12, is said to have a range of about 1,000 kilometers and is designed to threaten straits and approach routes while moving launchers between islands.

The U.S. NMESIS has a range of about 115 miles (approximately 185 kilometers) and can be rapidly deployed by small Marine Corps units. The U.S. Army's HIMARS will also be moved to Ishigaki Island, and Typhon medium-range missile launchers are scheduled to be brought to Okinawa. If these can be connected through a unified command and information network, the adversary will have to calculate threats not only from a single axis of naval vessels but also from multiple firepower axes launched from the islands.

The Reality Indicated by the Absence of Aircraft Carriers

This time, there is no expectation of participation from aircraft carrier strike groups, which were prominent in past exercises. Defense News reports that the USS George Washington has been redirected to the Middle East, shifting the focus of the exercise from naval air power to ground-launched systems. USNI News also reported that this Keen Sword is structured around the defense of the southwestern islands.

This does not signify a weakening of the Japan-U.S. alliance. Rather, it reflects a more stringent assumption that does not rely on the constant presence of aircraft carriers, instead enduring the initial days with dispersed firepower from the island regions. When separating capability from intent, the U.S. intent lies in the continuation of alliance defense, while the deployable vessels are influenced by crises around the world. This is why Japan is hastening the development of its own long-range firepower.

Logistics and Integration Tested More Than Range

However, deterrence cannot be established solely by the figure of 1,000 kilometers. In the island regions, fuel, ammunition, camouflage, repositioning, and alternatives for damaged roads and ports determine firing capability. The concerns expressed by Yonaguni Town regarding the use of large equipment in ports and roads indicate that friction between military planning and civilian infrastructure remains unresolved. Additionally, there are still questions about which Japan-U.S. units will share what target information and under what authority after detecting naval vessels.

According to Tanaka's perspective, the true test of Keen Sword 27 is not the range of missiles but the speed of Japan-U.S. decision-making and logistics functioning without the presence of aircraft carriers. The greatest blind spot in southwest defense lies not in the enemy's approach itself but in the time it takes to transform dispersed units into a single combat system.

References

• Defense News, October 5, 2026
• USNI News, October 6, 2026