“Frank Knox’s Fifth Column in Hawai’i: The U.S. Navy, the Japanese, and the Pearl Harbor Attack”

Secretary of Navy Frank Knox declared a week after Japan’s attack on Pearl Harbor that fifth columnist activities were partly responsible for the success of Imperial Japanese forces. Who and what he meant when he used the phrase “fifth columnist activities” is subject to debate. Most assume he was referring to all Japanese Americans or Japanese nationals residing in Hawai’i. But this essay, based on Knox’s personal correspondence, supplemented with the Pearl Harbor Attack hearings’ published reports, Judge Advocate General records, and the 14th Naval District Intelligence Officer reports, finds that Knox was referring to the Japanese Consul-General Office and a small handful of Japanese American assistants who voluntarily carried out the task of keeping the U.S. Fleet and military installations under surveillance, thereby contributing to the success of the Imperial Japanese attack.