Against the backdrop of the growing global awareness of the inhumanity of nuclear weapons and the stagnation of nuclear disarmament, on July 7, 2017, the Treaty on the Prohibition of Nuclear Weapons (TPNW) was adopted by 122 countries, over 60% of United Nations member states. These countries demonstrated their unequivocal determination to abolish nuclear weapons. Just over three years after that day, on October 24, 2020, the number of ratifying countries reached 50, which is the number required for the treaty to come into effect. Ninety days after that, on January 22, 2021, the treaty came into effect. 　The treaty refers to the suffering and harm caused to the hibakusha as well as the efforts made towards nuclear abolition through furthering the principles of humanity undertaken by the hibakusha, among others. 　The treaty prohibits under any circumstances such activities as developing, testing, manufacturing, acquiring, possessing, stockpiling, transferring, using or threatening to use nuclear weapons. 　The treaty stipulates that nuclear-weapon states can become its signatories based on the premise that they shall complete their commitment to eliminate nuclear weapons by a set deadline with verification conducted by a competent international authority. 　The treaty institutes the holding of meetings of States Parties as well as review conferences to discuss its operation, to both of which non-states parties and NGOs, among others, shall be invited. 　Within one year of the treaty coming into effect on January 22, 2021, the first Meeting of States Parties will be convened, to discuss the implementation and progress of the treaty. The Meeting is currently planned to be held in Vienna, Austria. 　In order to make this treaty highly effective, one future challenge is, first of all, the need to further expand the number of countries that ratify the treaty. It is also necessary to approach the nuclear weapon states and states under the nuclear umbrella that oppose the treaty, encourage them to participate in the Meeting of States Parties and thus participate in the discussions concerning the treaty's effective implementation, and request that they join the treaty as soon as possible. Mayors for Peace, which has its secretariat in the Hiroshima Peace Culture Foundation, will work to further expand its member city network, which currently has more than 8,000 cities in 165 countries and regions, and will implement initiatives to develop peace awareness through implementing a 'peace culture' rooted in civic society that encourages each individual citizen to think about and act on peace in their daily lives. By doing so, Mayors for Peace will create a major momentum for peace, to support policy shifts by policy makers, to achieve a world without nuclear weapons.

Ceremony commemorating the TPNW coming into effect

　To commemorate the Treaty on the Prohibition of Nuclear Weapons coming into effect on January 22, on the following day, January 23, Mayors for Peace and civic organizations jointly held an online commemorative event named 'The End of Nuclear Weapons has begun!', linking the three cities of Hiroshima, Nagasaki and Tokyo.
　At the Tokyo venue, there were video messages shown from representatives of the United Nations and other related organizations, who had greatly contributed in bringing the treaty to this point.
　At the Hiroshima venue, the commemorative event started with Hiroshima Mayor Matsui, President of Mayors for Peace, together with Hiroshima Governor Yuzaki and two representatives of atomic bomb survivors (hibakusha) associations stating "Let's spread the message throughout the world that we do not need nuclear weapons, and create a peaceful society of coexistence together." Next, five young people made presentations on their own peace activities, which they are conducting having taking on the wishes of the hibakusha. They commented on each other's activities and discussed their ambitions for the future, renewing their determination saying "We of the younger generations must succeed the wishes of the hibakusha and take action." This was followed by video messages from representatives of peace related organizations, after which there was a recital of atomic bombing poetry, backed by a guitar performance, by atomic bombing testimony recital volunteers. The event ended with a screening of a video performance of a chorus of peace songs by elementary school children.
　At the Nagasaki venue, there were interviews with young people and representatives of hibakusha associations, followed by a dialogue between the mayor of Nagasaki and others on methods that can be used to secure the TPNW greater recognition in international society.
　At the end of the commemorative event, all of the online participants at all the venues pledged to continue to push forward together with efforts aiming for a world free of nuclear weapons. 　Mayors for Peace will continue to aim for the development and expansion of global opinion for the abolition of nuclear weapons, through various joint initiatives with member cities. The coming into effect of the Treaty on the Prohibition of Nuclear Weapons represents a fresh start for these activities.