American Black Chamber

The first American peacetime codebreaking agency, closed in 1929

Overview

Herbert Yardley ran the Cipher Bureau, known as the Black Chamber, in New York after the First World War with State Department and Army funding. Its greatest coup was reading Japanese diplomatic traffic during the Washington Naval Conference of 1921 and 1922, letting American negotiators know how far Tokyo would bend on warship ratios. Secretary of State Henry Stimson withdrew funding in 1929, later summing up his view with the line that gentlemen do not read the mail of others. An embittered Yardley exposed its work in his 1931 book The American Black Chamber, causing a diplomatic sensation, while Army codebreaking continued under William Friedman.