A framework for understanding Islamic State of Iraq and al-Sham (ISIS)’s apocalyptic theology as an internal strategy to “coercively radicalize” its captive subjects is presented, by comparison to the Lord’s Resistance Army (LRA), which shares key stages of captive indoctrination with ISIS. A violent experience of “entry,” religious rules learned in an “assimilation” process, and millenarian “grand narratives” framing violence as purification, are examined. These stages construct an image of group leaders as divinely endowed with spiritual knowledge and access (i.e., charismatic authority). This can create a sense of dependency on the leaders and their instructions, potentially motivating violent and altruistic behavior from initially unwilling subjects.