A new survey of strategic elites in Japan and South Korea reveals deep skepticism toward nuclear weapons acquisition, but warns that a unilateral move by either nation could trigger a rapid shift in public and elite support in the other.
The findings, published Thursday by the Washington-based Center for Strategic and International Studies (CSIS), underscore the fragile balance between deterrence and proliferation risks in Northeast Asia. According to the survey, only 12% of Japanese respondents and 15% of South Koreans expressed support for developing nuclear weapons, with the majority citing economic costs, diplomatic isolation, and the stability risks of regional arms races as key deterrents.
Yet the data also highlights a critical threshold: if one country were to pursue nuclearization, the other would see a sharp uptick in domestic support. In Japan, 68% of respondents said they would back nuclear weapons if South Korea acquired them, while 62% of South Koreans indicated they would support Tokyo’s nuclearization in response. “This isn’t just about domestic politics—it’s about mutual reassurance breaking down,” said Michael Green, senior vice president for Asia at CSIS and a former National Security Council official under President George W. Bush. “Once one crosses that line, the other feels compelled to follow, even if they didn’t want to initially.”
The survey’s timing coincides with heightened tensions over North Korea’s advancing nuclear and missile programs, which have already prompted Japan and South Korea to accelerate their own defense reviews. In May, Japan’s government approved a record ¥43 trillion ($280 billion) defense budget for fiscal 2025, including funds for counterstrike capabilities—widely interpreted as a step toward de facto nuclear deterrence without formal weapons. South Korea, meanwhile, has expanded its submarine and hypersonic missile programs, with President Yoon Suk-yeol explicitly rejecting nuclear armament while leaving open the possibility of “all options” if North Korea’s threats escalate.
Why the survey matters
The CSIS findings align with a 2023 RAND Corporation study that predicted a 40% increase in South Korean public support for nuclear weapons if Japan pursued them, citing “security community” effects where regional alliances reinforce each other’s risk calculations. But the CSIS data goes further by quantifying elite-level reactions—a critical distinction, given that strategic decision-making in both countries is heavily influenced by military and bureaucratic circles rather than mass opinion.
Diplomatic sources in Seoul and Tokyo, speaking on condition of anonymity, confirmed that the survey’s conclusions have been shared with senior officials. “The message is clear: once you start down this path, the other side’s calculus changes overnight,” said one Japanese official familiar with the discussions. “That’s why both governments are trying to find non-nuclear ways to signal resolve.”
The survey also reveals generational divides. Among respondents under 40, support for nuclear weapons in both countries was nearly double that of their older counterparts, reflecting growing frustration with North Korea’s provocations and perceived U.S. reliability gaps. “Younger elites see nuclear weapons as a pragmatic tool, not an existential threat,” said Sheila A. Smith, senior fellow for Japan studies at the Council on Foreign Relations. “That’s a shift from the post-war generation’s absolute rejection of nuclearization.”
What happens next
Neither Japan nor South Korea has signaled immediate plans to develop nuclear weapons, but the survey’s implications are already shaping policy debates. In Japan, Prime Minister Fumio Kishida has faced pressure from the ruling Liberal Democratic Party to formalize nuclear deterrence options, while South Korea’s Yoon administration is navigating domestic backlash over its perceived tilt toward the U.S. on North Korea policy.
The U.S. response remains critical. A State Department spokesperson declined to comment on the survey but reiterated Washington’s stance that “the spread of nuclear weapons in Northeast Asia would be a grave threat to regional stability.” Behind the scenes, however, American officials have privately warned both allies that a nuclearized Japan or South Korea would complicate extended deterrence guarantees and risk triggering a broader regional arms race.
The next CSIS survey, expected in late 2025, will track whether elite skepticism persists—or whether the regional security environment has crossed the threshold into irreversible change.
