When Defense Secretary Donald Rumsfeld turned to special operations forces to take the lead in the hunt for Osama bin Laden five years ago, he no doubt had in mind the kind of kill-or-capture operation mounted to go after Pancho Villa, or, more recently, the Balkans' war criminals. The problem was that those manhunts came up empty. Finding a single individual intent on hiding, it turns out, is a very tall order, even for a superpower. In a rare interview, Lt. Gen. Dell Dailey, who has helped lead the hunt for al Qaeda's founder, explained why. "Our manhunting skills are...