Over the last 15 years, the literature on the impact of both the Iraq war and the September 11 terror attacks on the behavior of states and terrorist organizations has grown immensely. Despite this attention, there has been little research on how the invasion of Iraq impacted violent non-state actors (VNSAs), and particularly insurgent organizations killing of civilians and security personnel. Differentiating between the killing of police/military personnel and civilians is of key theoretical and policy importance, particularly if there are differences between the two in terms of insurgent behavior before and during the Iraq war. In this paper, we use the Big Allied and Dangerous Insurgency (BAADI) dataset to examine what factors impact the killing of police/military personnel and civilians by insurgent organizations between 1998 and 2012. We argue that before the invasion of Iraq, social and political factors influenced organizational lethality. During the Iraq war, however, we argue that this relationship changed because the United States and the West changed their policies and invested enormously in global resources to fighting non-state actors. Given this, the organizational factor that will determine an organization’s lethality would simply be the organization’s capability—captured most effectively by its size. Our analysis provides support for this argument.