No sooner had the Japanese bombers hit Pearl Harbor than a rumor spread that they had been guided by Hawaii's Japanese farm workers' slashing giant arrows in sugarcane fields. Similar stories swept California and beyond. "The fifth- column activities added great confusion," said Admiral Husband E. Kimmel, the Pacific Fleet commander. The confusion was largely his own.
Though there was no evidence of a single case of Japanese-American espionage throughout the war, FBI agents on the afternoon of Dec. 7 began to detain suspected "subversives." They swooped down on a Los Angeles baseball field, for example, to apprehend members of a...