Warlordism creates significant problems in failed states: it impedes the development of stable and secure societies, thwarts economic growth, and creates new threats to international security. Through a comparative study of four seemingly disparate cases—medieval Europe, Republican China, and Somalia and Afghanistan in the mid-2000s—it is possible to develop an inductive, generalizable definition of warlordism. Warlordism emerges when armed men seize small slices of territory in disintegrating states for their own benefit, using charisma and patronage ties to cement their local authority, and disrupting commerce and investment through their fragmentary rule. Two causal factors were necessary for the demise of warlordism in medieval Europe and Republican China: the presence of a powerful and aggrieved economic interest group, and the appearance of a transformative idea from outside the existing system that supported the interest group's actions. If this same causal relationship holds true today, then warlordism will be more quickly eliminated in Somalia than in Afghanistan. The international community can take action to help eliminate warlordism, but change ultimately depends on domestic factors and will likely be violent.