The Intelligence Failure of Pearl Harbor

^^J n a late summer morning in 1940, Frank B. Rowlett, a 32-year-old civilian employee of the U.S. Army, climbed into his Ford sedan in Arlington, Virginia, and drove to his job in Washington, D.C. Though his work was all but obsessive and tempted him to revert to it during his commute, Rowlett was disciplined and kept his mind on the traffic. He parked in a lot behind the Munitions Building, the army's offices on Consti tution Avenue, arriving at .7 a.m., an hour early, as was his custom. He walked down one of the wings that stretched out the back of the building like teeth on a comb. A steel gate and an armed guard blocked the entrance to Rooms 3416 and 3418. They were among the most secure in the entire struc ture, and the work that went on in them among the most secret in the U.S. government. Rowlett was a codebreaker; he had charge of the team trying to crack the most secret diplomatic cipher of the Empire of Japan, a machine that American cryptanalysts called PURPLE, and within hours on that day, Friday, September 20, he would be celebrating one of the greatest moments in American cryptology.