Humans, and perhaps their pre-human ancestors, have engaged in murder and mayhem, as individuals and in groups, for hundreds of thousands of years. And, at least since the advent of recorded history, violence and politics have been intimately related. Nation-states use violence against internal and external foes. Dissidents engage in violence against states. Competing political forces inflict violence on one another. Writing in 1924, Winston Churchill declared—with good reason—that “the story of the human race is war.”