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. This article presents a framework for studying the internal management strategy of the so-called Islamic State of Iraq and al-Sham (ISIS). It is asserted here that to understand ISIS's internal approach, we must examine the combined effects of (1) its violent recruitment, (2) its religious behavioral rules, and (3) its apocalyptic narrative. There is regular recourse to comparative examples when researching what makes non-state armed groups work. Naturally, it is tempting to compare ISIS to its Islamist forebears such as Al Qaeda when doing so. However, the above traits have been well documented in another religious armed group that serves as an enlightening comparison, all the more so because it is not an Islamist movement.