The threat posed by the Islamic State[1] is frequently described as unprecedented and unique. Measured by the size of territory it once controlled, its wealth in terms of cash on hand and access to modern military material, and in its shocking brutality, the Islamic State has broken new ground as a terrorist organization. However, the Islamic State is not simply a terrorist organization, but is also a well-equipped insurgent army, and a quasistate that seized and–with qualified success–operated the bureaucratic institutions of the territories it captured. The Islamic State is often contrasted with its ideological predecessor and operational competitor, al-Qaeda. Highlighting how these organizations differ is helpful in developing effective means of confronting them. In this article, we compare the Islamic State to another terrorist organization the Sendero Luminoso of Peru, to help understand the forces that gave rise to them, sustained them, and ultimately led to Sendero’s demise. Through this comparative analysis, we argue that understanding the Islamic State, not simply as a terrorist organization but also as a social movement, allows us to contextualize its violence within patterns evinced by other violent social movements. This approach will also allow us to better understand how the Islamic State might eventually end. Although the military defeat of the Islamic State may be inevitable, the socio-political conditions that gave rise to and sustained it will likely remain and its remnants may very well present a “traditional” terrorist threat for years to come.