Joe Rochefort's War: The Odyssey of the Codebreaker Who Outwitted Yamamoto at Midway

摘要

Joseph Rochefort was the head of Hypo, the Sigint unit at Pearl Harbor, from mid-1941 to fall 1942. He had enlisted in the US Navy in 1918, and risen through the ranks. He served as a cryptanalyst from 1925 to 1927 in the new codebreaking unit, Op-20-G, after which he deliberately kept away from Sigint, which was a career killer. From 1929 to 1932, he lived in Japan to learn the language. His unique qualifications as a cryptanalyst and Japanese language expert, combined with a background in fleet intelligence and communications, made him an ideal choice to run Hypo in June 1941. Rochefort had then been away from cryptanalysis for 14 years. Despite the book's sub-title, he therefore did not work as a codebreaker at Hypo, but as a skilled crypto-linguist and intelligence analyst. Until December 1941, Hypo was forbidden by Op-20-G to attack JN-25, the principal enciphered code of the Imperial Japanese Navy (IJN), which was slowly being solved by Op-20-G and Station Cast in the Philippines. Instead, Hypo was assigned the little used IJN Flag Officers' code. It was a hopeless task, and a bad mistake by Captain Laurance Safford, the head of Op-20-G, since too few messages were being intercepted to allow its solution. In consequence, Hypo could only use traffic analysis and direction-finding to track the Japanese fleet, and so was unable to give any warning of the attack on Pearl Harbor.