Japan's Nuclear Submarine Debate Resurfaces as Security Pressures Mount

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Kaiji Kawaguchi's hit manga The Silent Service, published in the nineties, begins with a dramatic premise. Japan's first nuclear-powered submarine, the Yamato, declares itself an independent state and turns its guns on the world.

In one of its most famous scenes, the Yamato sends a chilling radio message to the United States Navy: "Good morning, USA. This vessel is sailing under nuclear power." The line was inspired by a real event — when the world's first nuclear submarine, the USS Nautilus, sent a similar transmission as it cruised down the Thames River in 1955.

In the story, the Yamato takes on both the US and Russian navies single-handedly, even breaching the surface like a white whale to dodge enemy fire. Much of the manga's power lies in the realism of its protagonist, a nuclear submarine capable of remaining submerged almost indefinitely. It boasts far greater endurance and combat capability than any conventional vessel.

From Fiction to Possibility

While it once existed only in fiction, a nuclear submarine bearing Japan's Hinomaru flag is now entering real-world debate. A report released on September 19 by the Ministry of Defense Expert Panel on the Fundamental Reinforcement of Defense Capabilities set the debate in motion. Chaired by former Keidanren president Sadayuki Sakakibara, the panel called for reviewing options that include nuclear propulsion.

The report calls for examining the acquisition of long-range submarines, including the potential adoption of nuclear propulsion. These would not be nuclear-armed "strategic submarines" for deterrence, but "attack submarines" designed to hunt and destroy enemy vessels.

Japan has, in fact, quietly debated the issue before. During the drafting of the 2004 Defense Program Guidelines, government officials secretly examined whether the country should develop nuclear-powered submarines to counter China's accelerating naval buildup. Ultimately, the idea was shelved, as the legal, budgetary, and operational hurdles were deemed insurmountable at the time.

Strategic Motivation

The renewed reference to nuclear submarines in 2025's expert report reflects growing momentum within the Ministry of Defense itself. In June, China's aircraft carrier Liaoning crossed the Second Island Chain, the defensive line linking the Ogasawara Islands and Guam, for the first time. Officials now expect the People's Liberation Army Navy to expand its operations more aggressively into the Pacific.

In the deep waters of the Pacific, nuclear-powered submarines, capable of remaining submerged for long durations and moving at high speed, hold a decisive edge. China already operates more than ten such vessels. As one senior Defense Ministry official put it:

"For Japan's Self-Defense Forces, which trail the Chinese military in both manpower and budget, nuclear submarines would be an extremely effective option."

*Aerial photograph of a mammoth China Coast Guard vessel in the South China Sea (provided by the Philippine Coast Guard via Kyodo)*

The envisioned Japanese subs would likely carry long-range, non-nuclear missiles. Although Japan is expanding its strike capabilities, ground-based systems remain vulnerable to preemptive attacks due to their fixed positions. By contrast, nuclear-powered submarines could serve as a potent deterrent: a mobile platform for counterstrike and survival.

High Hurdles Ahead

The government is reportedly considering revising its Defense Buildup Program ahead of schedule to determine whether nuclear-powered submarines should be part of Japan's future force structure. Within the Defense Ministry, one scenario under discussion envisions purchasing American-made submarines initially, followed by a gradual transition to domestic production.

Yet the challenges are immense. A single nuclear submarine costs over ¥1 trillion JPY ($6.7 billion USD), more than ten times the price of a conventional diesel-electric vessel. Even with swift approval, operational deployment would take more than a decade. Legal questions also loom large: Japan's Atomic Energy Basic Act limits the use of nuclear power strictly to peaceful purposes.

Old Fears, New Realities

Compounding these hurdles, there is little evidence that the Defense Ministry consulted other agencies or the LDP's pacifist coalition partner, Komeito, before the proposal surfaced.

When a Sankei Shimbun reporter asked a senior finance ministry official for comment, the reply was terse and telling:

"They're living in the past. It really makes you wonder what they're thinking."

Even if the vessels used nuclear power solely for propulsion, memories of the Mutsu incident, a radiation leak from Japan's experimental nuclear-powered ship in the 1970s, could easily resurface, stirring public unease.

Still, as China, Russia, and now North Korea push ahead with their own nuclear submarine programs, Japan's continued self-restraint is beginning to look increasingly out of step with the region's harsh security realities. A former administrative vice-minister of defense put it bluntly:

"The peaceful era when we could say, 'Our conventional subs are advanced enough, we don't need nuclear ones,' is long gone."

A nuclear submarine would not be a cure-all for Japan's defense challenges. Yet it could help close the widening power gap with China.

During the LDP leadership election on October 4, security issues barely surfaced. Under Japan's new prime minister, the time has come for a candid, taboo-free debate on the Yamato's future, and for the government to clearly explain its choices to the public.

(Read the report in Japanese.)

Author: Shusuke Takenouchi, The Sankei Shimbun

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