In July 2017, 122 states voted to adopt the Treaty on the Prohibition of Nuclear Weapons (TPNW). The new treaty prohibits the possession of nuclear weapons. Hailed by disarmament advocates as an important step in creating a global norm against nuclear weapons, the treaty is largely rejected by nuclear-armed states. This talk will chronicle the development of the TPNW and then explore the ways in which the United States, Russia, China, France, and the United Kingdom have sought to undermine this treaty and the movement behind it.