At least since Ernest May's influential (1973) ‘Lessons’ of the Past, students of American foreign policy have been conscious of the powerful hold that some analogies seem to have on the minds of decision makers. All of us can think of “Munich” and “Vietnam” as shorthand for a whole series of judgments that we rely on to work through the maze of foreign policy calculus. In the aftermath of the World Trade Center attack in September 2001, we heard reference to “Pearl Harbor.” And we can now anticipate that “9-11” will take its place as a marker for a set of lessons concerning the struggle against terrorism.