(CNN)Seventy-five years ago today, hundreds of Japanese bombers attacked the American naval base at Pearl Harbor. America's shock, and its grief for the more than 2,000 US military dead on this date of "infamy" led to overwhelming unity of purpose as we entered a world war.
Yet America's unity was matched by its profound fears about national security in the days after Pearl Harbor. Well before December 7, 1941, Americans believed that enemy spies and saboteurs lived among us. Some did, though not nearly as many as we imagined. In 1940, the FBI reportedly received 3,000 complaints or tips every day regarding acts against America's national defense.
