A successful attack with weapons of mass destruction could certainly take thousands, or tens of thousands, of lives. If the device that exploded in 1993 under the World Trade Center had been nuclear, or had effectively dispersed a deadly pathogen, the resulting horror and chaos would have exceeded our ability to describe it. Such an act of catastrophic terrorism would be a watershed event in American history. It could involve loss of life and property unprecedented in peacetime and undermine America's fundamental sense of security, as did the Soviet atomic bomb test in 1949. Like Pearl Harbor, this event would divide our past and future into a before and after. The United States might respond with draconian measures, scaling back civil liberties, allowing wider surveillance of citizens, detention of suspects, and use of deadly force.