It looks like Japan will finally cast aside its ban on hosting nuclear weapons—specifically, those of the United States.
Moving towards action she called for last year, Prime Minister Sanae Takaichi is reviewing the three principles that have kept Japan at arm’s length from nuclear weapons since 1967. The ban is the third of those principles, the other two holding that Japan must neither own nor produce nuclear weapons. (From: The Strategist. The Australian Strategic Policy Institute.)
Japan is responding to what it perceives as worsening security dynamics in the region, surrounded as it is by three nuclear powers—China, Russia and North Korea—all of which are engaging in aggressive behaviour.
A 14 November Kyodo news report citing government sources noted that any changes in the three principles would constitute a major shift in Japan’s security policy in line with the ‘tough security environment.’ According to the report, the Japanese government sees the ban on placement of nuclear weapons within its territory as ‘weakening the effectiveness of the nuclear deterrence provided by its ally, the United States.’ This is particularly relevant as the US considers developing a nuclear-armed sea-launched cruise missile, known as SLCM-N, to strengthen deterrence against China.
Japan’s third nuclear principle was a non-issue after the end of the Cold War, when the US withdrew its tactical nuclear weapons. But Tokyo may need to re-think its position if Washington seeks to field SLCM-Ns.
At an 11 November meeting of the lower house Budget Committee, a member of the opposition party Reiwa Shinsengumi, Mari Kushibuchi, asked Takaichi about her plans regarding the three nuclear principles. According to an Asahi Shimbun report, the prime minister merely stated that ‘the government maintains them as a policy guideline.’ She went on to add that ‘the review of the three documents will start from now. We are not yet at the stage where I can say what the descriptions will be.’
Takaichi has been openly critical of the principles, particularly the third, since before she became prime minister. In her 2024 book, she wrote that ‘Even if we continue to adhere to “not possessing” and “not producing” [nuclear weapons], the “not permitting the introduction” principle is not realistic if we expect the United States to provide extended deterrence. I was concerned that in an ultimate crisis, the wording “adhere to the three non-nuclear principles” would become an obstacle.’
This review is not unprecedented. The three non-nuclear principles have been adhered to through several decades, but a 2010 parliamentary debate showed that Japan had considered scenarios that could require a more flexible approach. At a March 2010 session of the House of Representatives Committee on Foreign Affairs, then foreign minister Okada Katsuya said, ‘If an emergency were to occur in which Japan’s security could not be protected without allowing a temporary nuclear port call, I believe that the administration in power at the time would have to make a decision that would put the fate of the administration on the line and explain it to the public.’
China’s nuclear expansion poses a challenge to the US’s extended deterrence, on which Japan depends. If China were to achieve nuclear parity with the US in the coming decade, Tokyo would have to worry that Washington’s commitment might falter. This will no doubt be an important consideration as Japan conducts its review.
Any shift in Japan’s non-nuclear principles could invite reactions from the region. China has already responded to news of Japan’s review. Chinese Ministry of Foreign Affairs spokesperson Lin Jian said on 14 November that China remained ‘seriously concerned over Japan’s military and security moves recently …. The Sanae Takaichi administration has been making ambiguous statements about the three non-nuclear principles and implying the possibility of quitting the principles.’ The spokesperson added that China was also concerned about the claims by senior Japanese officials that Japan ‘has not ruled out the possibility of possessing nuclear submarines.’
Regardless of the result of the review (if it is completed), persistent doubts around the US’s commitment to extended deterrence could push Japan to develop its own nuclear weapons. China’s ongoing and unbridled nuclear expansion and modernisation puts pressures on both Japan and South Korea. Therefore, despite Japan being a global champion of a nuclear-free world, it will need to confront the reality of an expansionist China that holds an expanded nuclear arsenal.
