Farhana Yamin, who advised the Marshall Islands, recounts why and how the High Ambition Coalition (HAC) was formed. Born out of the diplomatic disaster of COP 15 in 2009, where progressive countries had been “stuck in silos within their own coalitions”, the coalition grew in the context of the Cartagena Dialogue (CD) and the Climate Vulnerables Forum and was finally announced as “the HAC” in Paris. Representing a majority of parties, highly vulnerable countries, as well as major emitters, the coalition allowed for a Paris outcome that was more than just the lowest common denominator. Testifying to the HAC’s success, the Agreement came to include key demands of the vulnerable countries that had shaped it, including a temperature goal of 1.5°C. Yamin highlights the role of resources, networks, and relationships, which were formed at informal gatherings such as those in the CD. Assessing the overall HAC experience and impact, Yamin describes the demise of the HAC after COP 21 resulting from the failure of the EU and others to deliver or the election of Trump. She argues that the HAC was a time-bound strategic feature and that “next time there will be a different way of doing it”.