Following the terrorist attacks of September 11, 2001, the Bush administration established a security discourse based on the paradigm of “uncertain threats,” characterizing the “war on terror” as a war against the “unknown.” From the point of view of this new security discourse, counterterrorism should not confine itself to the accumulation of data concerning the goals, strategies, and means of terrorist networks. It also depends on ingenuity on the part of security analysts in the imagination of possible present and future events. Besides analyzing facts, counterterrorism has to work speculatively through possibilities, to think in the subjunctive. Consequently, members of the Hollywood entertainment industry were invited by the Pentagon in October 2001 “to brainstorm about possible terrorist targets and schemes in America and to offer solutions to those threats.” The present article argues that the consideration of fiction as potential fact is symptomatic of the discursive response to terror, which oscillates between the real (actual incidents of political violence) and the imaginary (anticipated further attacks), both drawing on and contributing to what I propose to conceptualize as the cultural imaginary of terrorism. Although this dynamic became particularly salient after 9/11, it has a much longer history, going back to the first emergence of sub-state violence against public targets at the close of the nineteenth century, when several literary writers devised spectacular scenarios of attacks from the air or with biological weapons. What distinguishes these late-Victorian fictions from post-9/11 counterterrorist discourse, however, is that the latter has made the imaginary an integral feature of homeland defense and thus a basis for political practice.