At the end of World War II atomic bombs were dropped on Hiroshima and Nagasaki, killing hundreds of thousands and leaving many others with life-long radiation illnesses. The survivors, called hibakusha, began sharing their experiences so the world could see the inhumanity of nuclear weapons. Founded in 1956, Nihon Hidankyo has organized petition drives, spoken at international conferences, and addressed the United Nations to call for a legal ban on nuclear arms. By placing real human suffering at the center of the debate, they strengthened global opinion that nuclear weapons must never be used—a norm often referred to as the nuclear taboo. This bottom-up civil movement earned the group the 2024 Nobel Peace Prize.

While Nihon Hidankyo began as a domestic support network for survivors, it gradually evolved into a transnational advocacy actor shaping disarmament policy. By sharing epidemiological data from Hiroshima and Nagasaki with scientists, the group provided empirical evidence of long-term radiation effects, informing international humanitarian law and arms-control regimes. Its multilingual distribution of survivor testimonies, films, and exhibits employed a comparative public-relations strategy to frame the ‘inhumanity of nuclear weapons’ for audiences with diverse cultural and religious backgrounds. During negotiations of the 2017 Treaty on the Prohibition of Nuclear Weapons (TPNW), Hidankyo cooperated with ICAN and the Red Cross, dispatching survivor delegates who successfully inserted language on victim assistance into the final text. Scholars now cite this practice as a prime example of “testimonial diplomacy,” illustrating how lived experience can exert normative power in global politics.

Through campaigns to revise the Hibakusha Aid Law (1995, 2008) and by submitting statements to the UNGA First Committee, Nihon Hidankyo has been a central actor in constructing an evidence-based humanitarian disarmament discourse. Leveraging RERF epidemiological datasets, the organization presented policy-relevant risk assessments and highlighted the complementary value of qualitative survivor testimony to probabilistic exposure models such as DS02. From a norm-entrepreneurship standpoint, Hidankyo’s advocacy helped extend the nuclear taboo from a ‘use taboo’ toward a ‘possession taboo,’ influencing the comprehensive prohibitions codified in Article 1 of the TPNW. Network analyses of civil-society coalitions identify Hidankyo as a broker node within the ICAN hub, enhancing the efficiency of an expansive advocacy coalition. These dynamics offer empirical insights for theories of non-state norm creation and forum-shopping strategies in global governance.