„Roosevelt fought hard for the United States to host the opening session [of the United Nations]; it seemed a magnanimous gesture to most of the delegates. But the real reason was to better enable the United States to eavesdrop on its guests. Coded messages between the foreign delegations and their distant capitals passed through U. S. telegraph lines in San Francisco. With wartime censorship laws still in effect, Western Union and the other commercial telegraph companies were required to pass on both coded and uncoded telegrams to U. S. Army codebreakers. Once the signals were captured, a specially designed time-delay device activated to allow recorders to be switched on. Devices were also developed to divert a single signal to several receivers. The intercepts were then forwarded to Arlington Hall, headquarters of the Army codebreakers, over forty-six special secure teletype lines. By the summer of 1945 the average number of daily messages had grown to 289,802, from only 46,865 in February 1943. The same soldiers who only a few weeks earlier had been deciphering German battle plans were now unraveling the codes and ciphers wound tightly around Argentine negotiating points.
During the San Francisco Conference, for example, American codebreakers were reading messages sent to and from the French delegation, which was using the Hagelin M-209, a complex six-wheel cipher machine broken by the Army Security Agency during the war. The decrypts revealed how desperate France had become to maintain its image as a major world power after the war. On April 29, for example, Fouques Duparc, the secretary general of the French delegation, complained in an encrypted note to General Charles de Gaulle in Paris that France was not chosen to be one of the "inviting powers" to the conference. "Our inclusion among the sponsoring powers," he wrote, "would have signified, in the eyes of all, our return to our traditional place in the world." In charge of the San Francisco eavesdropping and codebreaking operation was Lieutenant Colonel Frank B. Rowlett, the protégé of William F. Friedman. Rowlett was relieved when the conference finally ended, and he considered it a great success. "Pressure of work due to the San Francisco Conference has at last abated," he wrote, "and the 24-hour day has been shortened. The feeling in the Branch is that the success of the Conference may owe a great deal to its contribution."
The San Francisco Conference served as an important demonstration of the usefulness of peacetime signals intelligence. Impressive was not just the volume of messages intercepted but also the wide range of countries whose secrets could be read. Messages from Colombia provided details on quiet disagreements between Russia and its satellite nations as well as on "Russia's prejudice toward the Latin American countries." Spanish decrypts indicated that their diplomats in San Francisco were warned to oppose a number of Russian moves: "Red maneuver... must be stopped at once," said one. A Czechoslovakian message indicated that nation's opposition to the admission of Argentina to the UN.
From the very moment of its birth, the United Nations was a microcosm of East-West spying. Just as with the founding conference, the United States pushed hard to locate the organization on American soil, largely to accommodate the eavesdroppers and codebreakers of NSA and its predecessors.“
Body of Secrets: Anatomy of the Ultra-Secret National Security Agency from the Cold War Through the Dawn of a New Century