When John Jester addresses military and civilian law enforcement agencies throughout the country, he offers two key pieces of advice: first, don't think it can't happen on your watch, and second, think about the unexpected. And Jester is just the man to deliver such advice. He was chief of what was then the Defense Protective Service on Sept. 11, 2001, when a hijacked airliner crashed into the Pentagon. It was a day and an event that forever transformed the way he thinks about security. It also was a day and an event that helped him transform the present- day security...