This is an open access title available under the terms of a CC BY-NC-ND 4.0 International license. It is free to read at Oxford Scholarship Online and offered as a free PDF download from OUP and selected open access locations. The Egyptian al-Jama'a al-Islamiyya and Islamic Jihad have shaped the trajectory of jihadi salafism since its inception and defined a key strategic divide between mass-movement mobilization and elitist avant-gardism. Despite their shared histories, however, al-Jama'a al-Islamiyya rejected al-Qaeda's transnational violence and became a political party after 2011, whereas Islamic Jihad has formed the backbone of Osama bin Laden's organization. These strategic divergences are puzzling since these groups emerged in the same country around congruent ideologies. Institutionalizing Violience develops an institutional approach to radicalization to compare the two groups' comparative trajectories. It is based on extensive field research conducted with their leaders and members in Egypt. The interviews provide a unique perspective on how jihadi groups make and implement new strategic decisions in changing environments, as well as the evolution of their approaches to violence and non-violence.