Adopted by 122 non-nuclear-weapon states in July 2017, the Treaty on the Prohibition of Nuclear Weapons (TPNW) was promoted by a transnational network of government agencies, international organizations, and civil society actors. Now, as the agreement creeps towards entry into force, a debate about the history of the TPNW has begun. While supporters of the TPNW argue that the adoption of the treaty was a reasoned response to diplomatic impasse and the pileup of empirical evidence on the humanitarian consequences of nuclear detonations, revisionists have argued that the humanitarian initiative was never about banning nuclear weapons, but was hijacked by radicals eager to shame the Western nuclear powers or discredit the NPT. Reading the TPNW as a manifestation of "frustration" with lacking progress on disarmament in other forums, observers have framed the adoption of the TPNW as an irrational outburst of emotions. In this article, I investigate Norway's nuclear disarmament diplomacy in the period from 2005 to 2013. Against the revisionists, I argue that the goal of negotiating a new legal instrument outlawing nuclear weapons provided a key aim for the Norwegian centre-left coalition government from 2010 onwards. Drawing on elite interviews, internal MFA documents released on freedom of information requests, and official statements by foreign policy officials, I maintain that the humanitarian initiative, including the pursuit of a new legal instrument, was products of a carefully deliberated policy of strategic social construction.