Japan Opens Debate on Nuclear Subs and Port-Call Exceptions
Takaichi says Japan will weigh nuclear-powered subs and a port-call exception to its non-nuclear principles; China accuses Tokyo of nuclear ambitions.
October 16, 2026 — Japan’s prime minister has opened two nuclear questions that previous governments kept closed. Speaking to the House of Representatives Budget Committee on October 14, Sanae Takaichi said her government will consider nuclear-powered submarines for the Self-Defense Forces “in a concrete and realistic manner,” Kyodo News reported. In the same session she said a 2010 statement on emergency port calls by U.S. nuclear-armed ships leaves “room for consideration,” according to The Herald Business.
Neither step changes policy yet. Both feed into the rewrite of Japan’s three core security documents, which the cabinet plans to finish by the end of the year.
Two questions, one review
The first question is propulsion. Japanese law limits nuclear energy to peaceful purposes, and past governments held that it cannot power SDF submarines, Kyodo noted. Takaichi told lawmakers earlier in October that “nothing is decided at this point.” On October 14 she called stronger surveillance in the Pacific an “urgent” task and said Tokyo would take into account developments in partner countries such as Australia and South Korea.
The second question is the third of Japan’s Three Non-Nuclear Principles: not possessing, not producing and not permitting the introduction of nuclear weapons. The 2022 National Security Strategy says Japan will keep “observing the Three Non-Nuclear Principles.” In 2010, then-Foreign Minister Katsuya Okada told the Diet that if Japan’s security could not be protected without letting U.S. nuclear-armed vessels into port, the government of the day would “stake its political fate on making that decision and explaining it to the public,” The Herald Business reported.
Foreign Minister Toshimitsu Motegi backed a review on October 14. “While we maintain the three non-nuclear principles, there is a need to conduct a review based on the dramatically changed security environment and threat perceptions within that framework,” he said, as quoted by The Herald Business. Takaichi declined to say what wording the new documents will use: “I would refrain from prejudging that.” She repeated that hosting U.S. nuclear weapons under a “nuclear sharing” arrangement “is not something Japan is currently considering, nor is it appropriate.”
Where each issue stands
| Issue | What was said | Status |
|---|---|---|
| Nuclear-powered submarines | Takaichi, Oct 14: will consider it “in a concrete and realistic manner” | Leading option is a pledge to study new power sources (Asahi) |
| Introduction ban (port calls) | Takaichi: Okada’s 2010 remark leaves “room for consideration”; Motegi backs a review | Government plan reportedly keeps the principles and adds the Okada remark (Asahi, via The Herald Business) |
| Possession and production bans | No change proposed | Unchanged; restated in the 2022 National Security Strategy |
| Nuclear sharing | Takaichi: “not something Japan is currently considering” | Not under consideration |
Compiled by Peter’s World from Kyodo News, The Herald Business, the Asahi Shimbun and Japan’s 2022 National Security Strategy, all linked in this article.
The case and the costs
Inside the government, the submarine debate is more cautious than the prime minister’s words suggest. The Asahi Shimbun reported on October 13 that the leading option is not a commitment but a pledge to “study” new power sources, including nuclear power, for submarines with vertical launch tubes for long-range missiles. Coalition talks on the wording could begin as early as November.
The Asahi laid out the hurdles. One nuclear submarine is said to cost about 1 trillion yen ($6.32 billion), and at least three would be needed to keep one ready at all times. Building them would likely take more than a decade, and the SDF is already short of people. “We do not have the manpower to spare for nuclear submarines,” a source close to the Maritime Self-Defense Force told the paper. Some former defense ministers call the idea unrealistic and say it would needlessly provoke neighbors. Adm. Akira Saito, the Maritime Self-Defense Force’s chief of staff, said such boats would bring a “dramatic improvement in capabilities.”
Politics pushes from the other side. Nippon Ishin, the junior partner in Takaichi’s coalition, wants early acquisition of nuclear submarines and a “realistic review” of the introduction ban, and Xinhua, citing the Nikkei, reported that Takaichi argued for revisiting that ban before she took office. In a book published before last year’s party leadership race, she wrote that the introduction ban “is not realistic if Japan expects the United States to provide extended deterrence,” The Herald Business reported.
Beijing’s response
China answered on October 16. Foreign Ministry spokesperson Mao Ning told reporters that “the remarks once again revealed Japanese authorities’ inflating ambitions of possessing nuclear weapons.” She accused Tokyo of seeking to “ditch the three non-nuclear principles” and said such moves “pose a serious threat to peace and stability in Asia and the wider world,” according to the ministry’s transcript. Takaichi has not proposed acquiring nuclear weapons; her stated positions concern propulsion and port calls.
What it means
Peter’s World analysis, based on the sources cited above.
The port-call question matters more in the near term than the submarines. The Herald Business, citing the Asahi, reported that U.S. submarines carrying the new nuclear sea-launched cruise missile (SLCM-N) could call at Japanese ports from the 2030s, and that Washington is said to view such visits as outside the meaning of “introduction.” Writing the Okada exception into the security documents would narrow that gap on paper without a formal change to the principles.
Nuclear propulsion is a longer, costlier bet, and the “study” wording would let the coalition defer it. The signal to watch is the final text of the documents in December: whether the principles are restated unchanged, restated with the Okada caveat, or reworded.
What to watch: coalition talks on the documents from November; any Defense Ministry cost study on submarine propulsion; Washington’s response to a port-call caveat; and whether Beijing escalates beyond statements.
Sources
- Kyodo News: Japan PM says to “seriously consider” introduction of nuclear subs (Oct. 14, 2026)
- The Herald Business: Japan’s Takaichi signals openness to easing nuclear weapons ban (Oct. 14, 2026)
- The Asahi Shimbun: Japan could add study on nuclear subs in security policy update (Oct. 13, 2026)
