Albigensian Crusade
Kurt Jonassohn and Karin Solveig Björnson describe the Albigensian Crusade as "the first ideological genocide". Kurt Jonassohn and Frank Chalk (who together founded the Montreal Institute for Genocide and Human Rights Studies) include a detailed case study of the Albigensian Crusade in their genocide studies textbook "The History and Sociology of Genocide: Analyses and Case Studies", authored by Strayer and Malise Ruthven.