Concerned about large-scale ship-building programs in the US, Great Britain, and Japan following World War I, US President Warren G. Harding organized the Washington Naval Conference in late 1921. The conference was held in Washington DC and nine nations attended. Harding's goal was to establish limits on the number and tonnage of warships of each nation. In addition to concerns of a naval arms race, Harding and other nations were concerned about Japanese expansion in the Pacific.Herbert Yardley's "Black Chamber," a civilian cryptography bureau funded jointly by the State Department and the US Army, intercepted and deciphered the communications of the participating countries' delegates. Over the course of a few months, Yardley's team deciphered or translated nearly 5,000 messages. Notably, shortly before the conference, Yardley's team had a major success when it broke the Japanese diplomatic code and learned of the Japanese government's instructions to its ambassadors. Naturally, knowing the lowest naval ratio the Japanese were willing to accept put the US in a powerful negotiating position.The Washington Naval Conference is hailed as the first disarmament conference in history and a successful one as well. The resulting treaties remained in effect until 1936 when Japan backed out. The role of the Black Chamber during the conference also had a significant impact on the field of signals intelligence. The Black Chamber enjoyed increased funding and support in the years following, and its chief, Herbert Yardley, received the Distinguished Service Medal. This support lasted until the Black Chamber was closed by Secretary of State Henry Stimson, in 1929.