Sept. 11, 2001, was one of the darkest days in modern U.S. history. The world suddenly changed — the most powerful nation on the planet found itself vulnerable to mass casualty attacks from small groups of suicidal fanatics.

Despite warnings from the U.S. intelligence community that an attack was imminent, President George W. Bush was caught on his heels, shocked and embarrassed at the worst assault on U.S. soil since Pearl Harbor. The White House committed itself to ensuring a similar attack never happened again. The attacks thus led to an extraordinary expansion of the national security state.