The New Reality of Defense for the Southwestern Islands with the Improved Type 12 in Keen Sword 2026

The distance from Yonaguni Island to Taiwan is approximately 110 kilometers. The Japan-U.S. joint integrated exercise Keen Sword 2026, scheduled from October 19 to 29, will reaffirm this distance as an operational reality. Approximately 45,000 personnel from the Japan Ground Self-Defense Force, along with forces from nine other countries, will participate, highlighting the concept of operating a dispersed missile network across the southwestern islands.

From Ship-Centric to Island Dispersal

The U.S. Marine Corps will deploy the NMESIS (Naval and Marine Corps Expeditionary Ship Interdiction System) and MADIS (Marine Air Defense Integrated System) on Yonaguni Island for the first time. The range of NMESIS is reported to be about 185 kilometers, representing the idea of placing anti-ship and air defense capabilities on each island without waiting for large platforms from the naval and air forces. The U.S. Army's HIMARS will move to Ishigaki Island, and the medium-range missile Typhon is also expected to be transported to Okinawa.

Japan's Range of 1000 Kilometers

The Japan Ground Self-Defense Force will incorporate the improved Type 12 surface-to-ship guided missile, known as the Type 12 Improved or Type 25 surface-to-ship guided missile, which is set to be deployed to the southwestern islands starting at the end of fiscal year 2025. Its range is said to exceed that of the conventional type significantly, at approximately 1000 kilometers, and when combined with the Type 88 surface-to-ship guided missile and the Type 03 medium-range surface-to-air guided missile, it can form a denial capability from the islands to the straits.

However, extending the range alone does not complete deterrence. If the information link for detecting, identifying, and confirming the effectiveness after launch is broken, long-range missiles become merely expensive ammunition. The core of Keen Sword lies not in increasing the number of launchers on each island, but in how quickly the sensors and command systems of Japan and the U.S. can be connected.

Strengthening Alliances and Island Burdens

The absence of aircraft carrier strike groups is also a notable feature this time. The focus has shifted from the presence of large vessels to exercises that disperse mobile missile units across multiple islands. This is rational in the context of ongoing activities by Chinese Coast Guard vessels and naval ships around Taiwan, but it simultaneously deepens reliance on civilian ports, roads, and airports. The concerns of Yonaguni Town regarding the impact on transport vehicles and residents' lives are exploiting the weaknesses of military planning.

In my view, the true constraint on southwestern defense is not the number of missiles, but the logistics and the acceptance by local governments. While dispersed deployment is resilient against attacks, it cannot be sustained without protecting fuel, maintenance, and communications for each island. Keen Sword 2026 indicates that the Japan-U.S. alliance has shifted from exercises showcasing maritime superiority to designing for prolonged warfare, including civilian infrastructure. Who will bear that burden in peacetime has yet to be sufficiently discussed.

Key Sources

• Defense News (October 5, 2026)
• USNI News (October 6, 2026)
• Zona Militar (October 7, 2026)