Anti-Submarine Training with JMSDF Ise and US, India, Australia Vessels at Malabar 2026: Testing the Undersea Connectivity of the Japan-U.S. Alliance

On November 5, the opening ceremony of Malabar 2026, involving Japan, the U.S., India, and Australia, was held aboard the Japan Maritime Self-Defense Force (JMSDF) destroyer "Ise," docked in Yokosuka. The training area is located south of Kanto and includes anti-submarine operations and surface fleet engagements until the 12th. Admiral Katsushi Omachi, Commander of the JMSDF Self-Defense Fleet, who attended the opening ceremony, stated that the security environment in the Indo-Pacific has become more complex, making cooperation with allied nations increasingly important. According to local reports from Kyodo News and announcements from the JMSDF, the participating vessels include "Ise" and "Mogami" from the JMSDF, a dock landing ship from the U.S. Navy, and frigates from India and Australia.

Focus of Training Not Reflected in Numbers

"Ise" is a helicopter-equipped destroyer with a length of 197 meters and a standard displacement of approximately 13,950 tons, suitable for wide-area anti-submarine surveillance using SH-60K and other aircraft. On the other hand, "Mogami" is a crew-reduced destroyer with a length of 133 meters and a standard displacement of about 3,900 tons, expected to share sensor information while covering a wide maritime area. Considering the publicly announced figures from the Acquisition, Technology & Logistics Agency and the differences in ship types, this training is not merely a fleet display. It will test whether the air operations of large vessels, the dispersed deployment of frigates, and the supply and transport capabilities of landing ships can be connected into a single maritime network.

Quad's Capabilities Tested Underwater for the First Time

Malabar began in 1992 as a bilateral exercise between the U.S. and India, with the JMSDF participating since 2007. The political positions of the four countries are not identical, and it is premature to view the Quad as a collective defense mechanism like NATO. However, in anti-submarine warfare, practical matters such as sharing acoustic information, communication procedures, transferring contact targets, and minimizing time differences between aircraft and vessels are more effective than political joint statements. Given the expansion of the Chinese Navy's submarine activities into the Pacific, training in the southern Kanto region will serve as a testing ground directly linked to the defense of the Nansei Islands and SLOC (Sea Lines of Communication).

Overlooked Risks for the JMSDF

However, increasing the number of participating vessels and acquiring continuous anti-submarine surveillance capabilities are separate issues. If the maritime conditions, communication secrecy, and engagement rules of each country differ, the connectivity established during peacetime training may not be maintained in a crisis. In the author's view, the metrics for measuring the success of this exercise should not be "how many vessels participated," but rather who shared detection information and in what timeframe, and how errors in contact were eliminated. The true weakness may not lie in the number of vessels but in the speed at which underwater information is delivered to political decision-makers.

Main Sources of Information

• Kyodo News "Quad nations begin joint naval exercise amid China's growing assertiveness" (November 5, 2026)
• Japan Maritime Self-Defense Force "About Japan-U.S.-India-Australia Joint Exercise (Malabar 2026)" (Announced October 27, 2026)
• USNI News "U.S., Partner Nations to Hold Annual Malabar Naval Exercise Near Japan" (October 29, 2026)