Mass killing (often carried out in the form of genocide) offends the sensibilities of many people around the world. It is considered a “crime against humanity,” such is its barbarity and ruthlessness. When it occurs, the question often asked by both victims and bystanders is, “Why?” I argue in this paper that mass killing is not, as is often portrayed, the result of primal bloodlust or racism. Through an examination of the Third Punic War, the Boer War, World War II, and the Rwandan genocide, I show that mass killing is actually carried out as a rational means to a political end; that is, it is simply politics by other means. If mass killing is a combination of politics and lethal violence, however, can it be called war? I argue that mass killing, while bearing similarities to and often occurring simultaneously as warfare, is nonetheless different from war because it does not require multiple sides actively fighting each other, as war does.