SIS’s solution of the extremely complicated Japanese machine cipher called "Purple" is considered by many to be one of the greatest achievements in the annals of military intelligence.
The intelligence derived from "Purple" was known as "Magic" and was closely held. "Magic" allowed top U.S. policymakers to track the whole course of Japan’s most secret diplomacy, up to the attack on Pearl Harbor.
Rowlett joined the SIS when it was less than a month old and consisted of three persons: Friedman, the SIS director, widely known as one of the world’s leading authorities on cryptology; an Army captain; and a secretary.
Their mission was to prepare the Army’s codes and ciphers, to intercept and analyze foreign code and cipher communications in peacetime, and to conduct the training and research necessary to become immediately operational should war break out. By the end of the same month, Rowlett was joined by two other junior cryptologists, Solomon Kullback and Abraham Sinkov.
Rowlett was placed in charge of the Army’s work on Japanese diplomatic intercepts. In 1939, he supervised the team of code-breakers, who, after 18 months of effort, cracked Japan’s highest level diplomatic cipher system.
Recalling those exciting early years, he later wrote: "With the solving of ‘Purple’ came pressure from G2 to fully exploit traffic on the Tokyo-Berlin and Tokyo-Rome circuits. A machine for deciphering ‘Purple’ was given to the Navy, another was sent to the Philippines, and one was given to the British. ‘Magic’ soon began to reach the highest levels of the government, including the president. ‘Magic’ provided some of the best intelligence available on Japanese plans during the year before Pearl Harbor. If America was not warned of the attack in time to prepare for it - and the reasons for this are still debated - the fact remains that ‘Magic’ did reveal that war was imminent. Throughout the war, it continued to provide a unique look at the diplomatic background of Japanese strategy and plans."
"Magic" helped U.S. forces in the European theater as well. By reading messages from the Japanese ambassador in Berlin, the SIS provided American forces a detailed description of German fortifications along the Normandy coast. So valuable was this information to Allied invasion planning that when Gen. Dwight Eisenhower visited Arlington Hall Station after the war, he asked to meet the people who had produced the intelligence, so he could thank them personally.
The SIS laid the foundation for the massive cryptologic organization of today. By the end of the war, the Army controlled a worldwide network of intercept stations. In 1945, the U.S. Army Security Agency (ASA), predecessor to the Intelligence and Security Command, was set up to conduct all Army signals intelligence and communications security operations.
Rowlett saw the development of signals intelligence from its beginning in the Signal Corps, to its culmination in the establishment of the National Security Agency. He served in the Army from 1942 to 1946, rising to the rank of colonel. After the war, he became chief of the intelligence division of ASA, where he played a leading role in formulating policies establishing the Armed Forces Security Agency.
Rowlett served as technical director for operations in AFSA, and in 1952, he transferred to CIA, where for five years he was a senior staff officer and advisor to the DCI.
In 1958, he became special assistant to the director of the National Security Agency, a position he held under four directors. He led a study group that prepared the way for the founding of the National Cryptologic School, and in 1965, he became the school’s first commandant.
Rowlett’s contributions to U.S. cryptology were widely recognized. Among his many awards and honors are the President’s Award for Distinguished Federal Civilian Service, the National Security Medal, the Legion of Merit, and the Order of the British Empire. In 1964, Congress awarded him $100,000 as partial compensation for cryptographic inventions held secret by the government.
Recognition also came from Rowlett’s alma mater, Emory and Henry College in southwest Virginia, which awarded him the honorary degree of Doctor of Science.
Karen Kovach is the writer/editor in the history office at headquarters, U.S. Army Intelligence and Security Command, Fort Belvoir, Va.