Japan’s Prime Minister Sanae Takaichi formed a new cabinet under a Liberal Democratic Party–Japan Innovation Party coalition, naming Shinjiro Koizumi as Defense Minister. The administration plans to raise defense spending to 2% of GDP ahead of schedule and revise Japan’s 2022 National Security Strategy to counter China’s expanding military reach.

“We Will Not Rule Out Any Options”

In his first press conference on October 22, Koizumi said Japan is exploring “new types of energy sources for submarines” to strengthen deterrence.

He emphasized that no propulsion method, including nuclear energy, was being excluded at this stage. The remark marks the first open ministerial acknowledgment of nuclear-powered submarine discussions since 2004.

Ishin Japan coalition backs the development of “next-generation propulsion systems” for submarines capable of launching long-range missiles and sustaining deep-sea operations for extended periods.

Koizumi also endorsed revising Japan’s three principles on transfer of defense equipment, aiming to lift restrictions on exports of combat-related systems by 2026.

Expert Panel Recommends Nuclear Submarines

Koizumi’s comments follow a September 2025 report by the Defense Ministry’s Expert Panel on the Fundamental Reinforcement of Defense Capabilities, chaired by Sadayuki Sakakibara.

The panel advised Japan not to rule out nuclear propulsion and urged the acquisition of submarines capable of long-duration missions and non-nuclear long-range missile strikes.

The report noted that such vessels—costing roughly ¥1 trillion ($6.7 billion) each—could initially be imported from the United States before domestic production begins.

The plan addresses Japan’s limited defense manpower and budget by emphasizing endurance and survivability over sheer numbers.

“The Peaceful Era Is Long Gone”

As one senior Defense Ministry official described the shift starkly:

The peaceful era when we could say, ‘Our conventional subs are advanced enough,’ is long gone.

The comment captures Tokyo’s anxiety over China’s growing undersea fleet, now exceeding ten nuclear-powered submarines.

A senior Defense Ministry official added that nuclear-powered submarines would provide “an extremely effective option” for operations in deep Pacific waters, allowing higher speeds and longer submerged endurance than diesel-electric boats.

Legal, Financial, And Public Hurdles Remain

Japan’s Atomic Energy Basic Act restricts nuclear use to peaceful purposes, creating potential legal friction. Construction costs are over ten times higher than conventional submarines, with a timeline exceeding a decade per vessel.

Public sensitivity also lingers from past incidents, such as the 1970s Mutsu radiation leak, and the government has yet to consult pacifist coalition partner Komeito.

Still, proponents argue that nuclear propulsion would counter China’s push beyond the Second Island Chain and reinforce U.S.-Japan deterrence coordination.