Japan-U.S. Joint Exercise Keen Sword 26 Begins on October 19, Mobilizing 45,000 Personnel to Verify Defense of the Southwest Islands

On October 19, the Japan-U.S. joint integrated exercise "Keen Sword 26" will commence. According to the U.S. Naval Institute (USNI News), this Japan-U.S. exercise will primarily take place in Japan's southwestern region, where the U.S. military and the Self-Defense Forces will jointly train for island defense. The reported scale includes approximately 45,000 personnel from the Self-Defense Forces and the U.S. military, around 260 aircraft, about 40 ships, and approximately 6,100 vehicles. The exercise is expected to continue until October 29 and cannot be simply described as a ceremonial joint training.

The Reality of the Southwest Islands as Indicated by the Numbers

What is noteworthy about this scale is not just the number of participating units. In the defense of the Southwest Islands, air superiority, maritime transport, fuel and ammunition supply, and the restoration of damaged runways and ports must be handled simultaneously. The figures of 260 aircraft and 40 ships signify a shift from a peacetime base-centric operation to a concept of dispersing forces across multiple islands and regrouping them at necessary locations.

Even if the Ground Self-Defense Force units deploy to the islands, if the Maritime Self-Defense Force's escort ships and the U.S. Navy's transport and surface forces cannot maintain maritime traffic routes, the combat power will become isolated in a short period. Conversely, the more aircraft and ships are dispersed, the more shortages of fuel, maintenance personnel, and communication lines will become apparent. The success of the exercise should be judged not by flashy deployment scenes but by the continuity of supply over several days.

The Focus of the Japan-U.S. Alliance is Interoperability

The U.S. Navy announced that in August's "Pacific Vanguard 26," it conducted multilateral maritime training that included Japan's "Akizuki" class destroyer "Fuyuzuki," P-1 patrol aircraft, and submarines. Australia, Canada, New Zealand, and South Korea also participated, emphasizing multi-domain situational awareness and joint procedures. Keen Sword 26 will serve as a venue to connect this to practical command and control for the defense of the Japanese archipelago.

However, the weaknesses of the alliance are not limited to equipment shortages. If the rules of engagement, classification of information, and supply priorities differ between Japan and the U.S., decision-making on the ground will be delayed. Particularly in the Southwest Islands, it must be assumed that communications may be disrupted and that ports and airfields could be rendered unusable simultaneously. When separating capabilities and intentions, what will be confirmed this time is not Japan's defense will but whether the command centers of both countries can share the same situational picture in the initial stages of a crisis.

The Real Challenges Remaining After the Exercise

Even if Keen Sword 26 is successful, it does not guarantee that the temporary concentrated operations during the exercise can be transitioned to long-term SLOC (Sea Lines of Communication) protection in a crisis. In my view, the most easily overlooked aspect is not the number of ships and aircraft but the availability of replacement personnel and maintenance capabilities. There is a significant difference between being able to mobilize 45,000 personnel and maintaining a similarly sized force for several weeks. In this evaluation, not only the speed of deployment but also the procedures for maintaining combat power without withdrawal should be rigorously examined.

Reference Information

• USNI News, “U.S., Japanese Forces to Rehearse Defense of Japan's Southwest Islands”
• Zona Militar, “Japan will deploy 45,000 personnel and 260 aircraft...”
• U.S. Navy, “U.S., Allied Forces Join for Exercise Pacific Vanguard 2026”