New York had been attacked. The Pentagon just outside Washington D.C. had been attacked. Another plane had crashed a relatively short distance away in Pennsylvania. And there were other potential targets all around: the four pinch-point bridges across the Susquehanna River at Havre de Grace, Conowingo Dam, Aberdeen Proving Ground, the public water system, the many nearby nuclear power plants. By midday Sept. 11, 2001, a lot of things that seemed stalwart the day before seemed terribly vulnerable.