Japan Considers Nuclear Submarines, Strengthens Defense

Japan is entering a potentially important new phase in its defense discussions, openly considering military capabilities that would have been politically difficult to discuss just a few years ago. At the heart of this debate is the sensitive question of whether Japan should operate nuclear-powered submarines. This issue gained new attention after Defense Minister Shinjiro Kisumi confirmed that the government is not ruling out nuclear-powered submarines.

Defense Minister Shinjiro Kisumi continues his role under Prime Minister Sanae Takaichi following her September 17th cabinet reshuffle. He clarified that Japan has not yet decided to acquire nuclear-powered submarines, stating in a September 11th news conference that Tokyo would consider the option without reaching a predetermined conclusion. Kisumi highlighted that nuclear-powered submarines offer significantly longer submerged endurance and higher speeds compared to conventionally powered vessels.

Despite the advantages, significant challenges include the extensive maintenance and operating expertise required for nuclear-powered submarines, along with questions regarding their underwater quietness. Akira Gatada, a project lecturer at the University, emphasized that the Japanese government has not yet made a formal decision to procure these vessels, underscoring that nothing is finalized. A nuclear-powered submarine uses a nuclear reactor for propulsion, which does not inherently mean it carries nuclear weapons.

The current debate extends far beyond merely acquiring a different type of submarine, as Japan already operates a sophisticated conventional submarine force. Transitioning to nuclear propulsion would necessitate new technical expertise, extensive infrastructure development, specialized crews, dedicated maintenance facilities, stringent safety regulations, and potentially decades of investment.

The substantial financial investment required for nuclear-powered submarines is expected to be one of the biggest obstacles. Tokyo would need to clearly demonstrate that missions demanding the endurance and speed of a nuclear-powered submarine cannot be adequately performed by Japan's current or future conventional submarines. This examination is not isolated, as the regional submarine landscape is rapidly evolving. Australia, for instance, remains committed to the AUKUS arrangement with the United States and Britain, which aims to provide Australia with nuclear-powered submarines, as confirmed by Australian Prime Minister Anthony Albanese in August.

Under the AUKUS arrangement, U.S. Virginia-class submarines are expected to begin rotating through Australia in 2027, with plans for Australia to acquire its own nuclear-powered vessels in the following decade. South Korea is also advancing its own nuclear-powered submarine program, having announced plans earlier this year to launch its first such submarine by the mid-2030s while asserting compliance with its nuclear non-proliferation obligations.

In early September, North Korean leader Kim Jong Un attended the commissioning of the 5,000-ton-class destroyer Kang Khan, which Pyongyang claims will become part of its nuclear response system. This increasingly crowded strategic environment underscores why Japanese policymakers are exploring capabilities that offer greater endurance across the Western Pacific. China, however, views Japan's evolving defense posture with concern, repeatedly criticizing Tokyo's expanding military capabilities and its debate over nuclear-related policy.

In July, Chinese Foreign Ministry spokesperson Lin Jian criticized discussions surrounding nuclear-powered submarines and Japan's three non-nuclear principles, accusing the Japanese government of departing from post-war military restraints. Tokyo rejects Beijing's characterization of its defense buildup as a revival of militarism, asserting that its policies are intended to strengthen deterrence and national defense. The submarine debate is just one aspect of Japan's changing defense landscape.

Another significant development occurred in Okinawa, where Genta Koja, supported by Prime Minister Takaichi's Liberal Democratic Party and its allies, defeated two-term incumbent Denny Tamaki in the gubernatorial election on September 13th. Koja received approximately 59% of the vote, ending a 12-year period during which the Okinawa governorship was held by politicians opposed to the controversial U.S. base relocation plan. As governor-elect, Koja's victory is significant because Okinawa hosts the largest concentration of U.S. military facilities in Japan and holds strategic importance.

One of the most politically sensitive issues is the long-running plan to relocate U.S. Marine Corps Air Station Futenma from the densely populated city of Ginowan to a replacement facility in the Henoko area of Nago. While Tamaki opposed this relocation, Koja supports allowing the project to proceed. This does not mean that Okinawa's disagreements over the U.S. military presence have vanished. Concerns regarding aircraft noise, environmental effects, land use, and the overall burden created by military facilities remain major local issues, but the election alters the political relationship between Tokyo and Okinawa.

He cautioned against simplifying the contest as a choice between a supposedly pro-China candidate and an anti-China candidate. This distinction is important because the election was shaped by local economic concerns as well as the base issue. Koja's victory does not imply universal Okinawan support for Tokyo's broader defense agenda; however, the results could reduce one layer of political resistance to the central government's plans in Japan's southwestern islands.

Japan's southwestern islands have become increasingly important due to their proximity to Taiwan and the East China Sea. Yonaguni, Japan's westernmost inhabited island, lies only about 110 kilometers from Taiwan. Tokyo has already reinforced military deployments across the southwestern region, including missile and electronic warfare units. For Taiwan, Okinawa also holds potential significance in evacuation planning, logistics, and any wider regional emergency.

Shen Ming-Shih, a research fellow at Taiwan's Institute for National Defense and Security Research, highlighted that Okinawan authorities could become particularly important during a Taiwan Strait contingency. His comments represent strategic analysis rather than an announcement of any formal Japan-Taiwan defense arrangement, as Japan and Taiwan do not have a bilateral defense treaty. Concurrently, Japan is strengthening military coordination with established security partners, with Orient Shield 26 underway from September 24th, bringing together the Japan Ground Self-Defense Force, the U.S. Army, and the Australian Army.

The Japan Ground Self-Defense Force describes Orient Shield 26 as the largest such exercise held to date, encompassing activities from operational preparation to maritime transportation and joint airborne training. Joint airborne operations involving Japanese and American forces have occurred in Hokkaido, with Australian personnel also participating in the broader exercise. Russia has criticized these drills, particularly the presence of the U.S. Typhon mid-range missile system, arguing that its deployment on Japanese territory threatens Russian security.

Japan and its partners, in contrast to Russia's criticism, characterize exercises like Orient Shield as efforts to enhance readiness and interoperability. These exercises are taking place against a backdrop of increased Chinese and Russian military activity around Japan. Tokyo has expressed concern about closer strategic coordination between Beijing and Moscow, including naval operations in waters surrounding Japan. Japan has also been closely monitoring North Korea's ongoing missile and naval modernization programs.

The current security environment is marked by an overlap of several separate developments: Japan's submarine debate, increased defense spending, military deployments across the southwestern islands, deeper cooperation with the United States and Australia, North Korea's weapons development, and continued Chinese and Russian military operations in the region. Akira Gatada emphasized the importance of Japan demonstrating the strength of the Japan-U.S. alliance. He also highlighted Japan's expanding security cooperation with Australia, South Korea, the Philippines, and NATO partners.

For now, the nuclear-powered submarine question remains a debate, with Tokyo having not yet approved a purchase, selected a design, or announced a construction program. Defense Minister Kisumi's position is that Japan should study the option as part of a broader examination of necessary capabilities in a rapidly changing security environment. Okinawa's recent election adds another layer to this transformation, as Governor-elect Koja's victory could facilitate coordination between Tokyo and the prefectural government on certain defense issues, particularly the Futenma-Henoko relocation, despite ongoing local disputes.

Nuclear-powered submarines, long-range missile systems, stronger southwestern defenses, and larger multinational exercises are now being openly discussed or actively implemented. Whether all these ideas ultimately become permanent components of Japan's defense posture remains unresolved. However, with China, Russia, and North Korea continuing to develop their military capabilities, and Tokyo deepening cooperation with Washington and other partners, Japan is actively reassessing its security needs.