Japan weighs deploying unmanned submarines in Pacific defense buildup

The government is considering the full-scale development and deployment of unmanned submarines equipped with anti-ship strike capabilities as part of efforts to bolster Japan's defense posture in the Pacific, sources familiar with the matter said Saturday.

With China seeking to establish its maritime presence, Japan's defense posture has been criticized for having "gaps." The government is expected to explicitly state its "strengthening of response capabilities" in the Pacific in three security-related documents slated for revision by the end of the year, according to the sources.

The government is considering the introduction of unmanned submarines capable of carrying torpedoes and sea mines that could eventually travel long distances over extended periods. There is also a proposal to develop autonomous models equipped with artificial intelligence.

The government plans to deploy the unmanned submarines with manned destroyers and submarines as well as unmanned surface vessels equipped with missile launchers.

The Defense Ministry has allocated 100.1 billion yen ($619 million) in the budget for fiscal 2026 to establish "Synchronized, Hybrid, Integrated and Enhanced Littoral Defense," or SHIELD, to repel enemy attacks on far-flung islands, using large numbers of unmanned vessels.

The ministry plans to acquire small unmanned aerial drones for attack purposes as well as unmanned underwater vessels for intelligence gathering, in addition to the attack submarines.

The government will also consider establishing an air defense identification zone, or ADIZ, over the Ogasawara Islands in the Pacific, while planning to deploy surveillance and control radars to those islands in addition to Kitadaito Island on the Pacific side of Okinawa Prefecture.

There is also a proposal to reinforce the runway on Iwoto Island in the Ogasawara Islands, located around 1,250 kilometers south of Tokyo to allow more fighter jets to be deployed there.

While the aim is to address the gaps in Japan's defense posture and deter China, there is a possibility such efforts could further escalate tensions between Tokyo and Beijing.

Bilaterial ties have deteriorated since Japanese Prime Minister Sanae Takaishi made remarks suggesting Japan's potential involvement in a Taiwan contingency, angering China. China claimed the self-ruled island as part of its territory and aims to bring it under its control, by force if necessary.

The Senkaku Islands in the East China Sea, an uninhabited islet group controlled by Japan but claimed by China, have also been a source of tension between the East Asian neighbors.

In proposals compiled by the ruling Liberal Democratic Party for the government ahead of the revision of the three documents, the party, in apparent reference to China, noted that, "in the event of a protracted conflict, attacks against Japan could be launched from the Pacific side."

The proposals called for the integrated development of the Self-Defense Forces' response capabilities, command and control, and operational infrastructure.

According to defense experts, the Japan Maritime Self-Defense Force needs to maintain a state of vigilance along the Sea of Japan and around the Nansei Islands, where China and Russia are increasingly active, but it faces challenges due to personnel shortages. The Nansei Islands form the border between the East China Sea and the Pacific's Philippine Sea.

A senior Defense Ministry official said, "For a country surrounded by ocean on all sides, labor-saving and unmanned operations are essential for Japan's 'new way of fighting.'"

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