The treason trials after 1945 were shaped by Norway’s particular experience of German occupation. The central importance of Nasjonal Samling to German Nazification efforts in Norway meant that those planning for a post-war reckoning soon focused their attention on how to criminalise the actions of party members. This chapter outlines the course of the Norwegian occupation, including the manifold actions on the part of Norwegian citizens that would later give rise to punishment. It details how the exile government in London and the resistance forces in Norway jointly prepared the legal groundwork for the post-war reckoning. In doing so, this chapter highlights the reasoning behind the introduction of the extraordinary legal provisions that would both determine the course of the trials and cause significant controversy after the war.