Why do we fight? Have we always been fighting one another? Warfare is a topic that generates much thought, opining, scholarship, and debate. And it is easy to see why. Take a look at any major newspaper’s front page and you are likely to see at least a headline or two about conflict or violence happening somewhere on the globe. Such conflicts are occurring at various scales and involve disparate collections of people. Chances are that you know someone that has been affected either directly or indirectly by warfare. In academia, researchers from various disciplinary backgrounds continue to investigate, and theorize about, the ubiquity of violence and warfare in the recent and contemporary world. For this book, any actions related to collective violence between politically distinct groups of people can be considered part of warfare, whether they involve nation-states, tribes, village communities, nomadic bands, or even terrorist organizations. By warfare, we are referring to myriad forms of organized violence, whether they are massed armies on a battlefield, revenge killings between smaller-scale societies, or intervillage raiding related to feuding communities. With this sort of inclusive definition, one not biased toward modern forms of war, we believe researchers are much better equipped to give the topic fuller scrutiny.