September 11, when terrorists forcibly diverted two airline flights into the twin towers of the World Trade Center and a third plowed into the Pentagon, stunned surprise and inconsolable grief could be our only initial response. Then came an apprehension that will long be with us: how many other terrorist cells are still out there, and will we be able to find them in time?

But to many of those who have followed the scientific and technical side of warfare and terrorism, there was yet another jolt. It was comparable to the horror of the military analysts in December 1941 who had been expecting a Japanese preemptive strike in the Philippines or elsewhere in Asia, but not at Pearl Harbor. Assumptions were fatally wrong. Things were not supposed to be this way. We faced an old nightmare, not the futuristic dystopia of information warfare and massive chemical or biological attack that we had dreaded.