Japan Weighs Nuclear-Powered Submarines Amid Growing China, Russia Security Concerns

Japan’s government is weighing whether to begin a formal study on acquiring nuclear-powered submarines, a step that could feed into the country’s next scheduled revision of its national defense strategy, according to information obtained by Nikkei.

The idea is being discussed in Tokyo amid heightened security concerns in the region, particularly the expanding naval capabilities of China and increased military activity by Russia. Nuclear-powered submarines are viewed by some Japanese defense planners as a potentially valuable tool for sustained undersea operations, allowing vessels to remain submerged for long periods and travel farther without the need to surface frequently.

Any move toward examining such a capability would mark a notable development in Japan’s defense planning. While Japan already operates advanced diesel-electric submarines, nuclear propulsion would represent a significant shift in both technology and policy. Proponents argue that the endurance and range of nuclear-powered boats could help Japan monitor and deter activity in the vast maritime areas surrounding the country, including sea lanes critical to trade and energy imports.

The discussions come as Japan continues to update its security posture in response to a changing strategic environment. Tokyo has been strengthening ties with partners, expanding defense spending, and revising key policy documents in recent years to better address threats in the Indo-Pacific and beyond. A study on nuclear-powered submarines would likely be framed as part of that broader effort to reassess capabilities needed for deterrence and surveillance.

Still, substantial hurdles stand in the way. Domestic political sensitivities and practical constraints could complicate any attempt to pursue nuclear propulsion for military vessels. Japan’s postwar security framework, public attitudes shaped by the country’s history with nuclear weapons and nuclear energy, and questions about the industrial and regulatory requirements for operating nuclear-powered platforms all loom large.

At this stage, the government is considering only whether to launch an investigation, not making a decision to acquire such submarines. Even initiating a study, however, would signal that Japanese policymakers are willing to re-examine long-standing assumptions about the tools required for national defense in a more contested region.

A photograph accompanying the report showed the USS Kentucky, a nuclear-powered submarine, docking at South Korea’s Busan Naval Base, underscoring the growing visibility of nuclear-powered naval assets among U.S. allies in Northeast Asia.

Why it matters

If Japan proceeds even to an exploratory review, it could open a politically sensitive debate about how far the country should go in modernizing its military capabilities. Regional rivals and neighboring countries would likely scrutinize any shift toward nuclear propulsion, while Japan’s defense industry and regulators would face new technical demands. The next update to Japan’s security strategy will be a key moment to watch for signs of whether the proposal gains momentum or remains a conceptual option.