September 11 changed the United States’ understanding of terrorism. Prior to these attacks, Americans typically viewed terrorist events and actors through the lens of foreign affairs, quite removed from “everyday” concerns. Terrorist events involving Americans did occur, occasionally on American soil, but a sense of American invulnerability never truly wavered. September 11 challenged this presumption; as well as perspectives on the history of terrorism, compelling some to reexamine past events in order to find portents of the future tragedy.