In 2004, history was introduced by a Parliamentary decision as a new core subject in the Swedish upper secondary school system. This event constituted a major break--history now became a compulsory subject for all upper secondary school students after having been subject to a continually diminishing number of teaching hours ever since 1945. This surprising change forms the puzzle that this article seeks to address. Based on interviews and documentary analysis, we map and interpret the decision-making processes that ended with the Parliamentary decision to make history a new core subject. We add to existing insights about curriculum change by interpreting the process in terms of negotiation, persuasion, and framing and by linking actor strategies to structural--ideational and material--changes that created a window of opportunity for policy entrepreneurs. (Contains 2 footnotes.)