In the spring of 1929, the new Secretary of State under President Herbert Hoover learned that tucked away in New York City, his department was operating one of the world’s foremost code breaking operations. Led by legendary code breaker Herbert O. Yardley, the “Black Chamber” had been operating for almost 10 years. And despite a minuscule budget (less than $350,000 in a decade) and staff, the Black Chamber delivered more than 45,000 decrypted messages to American leaders. Perhaps their most important work came during the Washington Naval Conference in 1921/22. The Black Chamber’s delivery of decrypted negotiating instructions from foreign capitals to their delegates gave U.S. negotiators a decisive edge in crafting the eventual 5:5:3 naval force ratio that resulted. America’s supposed allies of the time, Great Britain, Italy, France, and Japan, among others, had no idea that U.S. negotiators effectively knew the parameters of their negotiating strategies.

Ironically, the Washington, D.C., bureaucrat that eventually authorized the funding and personnel to create MAGIC was the same idealistic gentleman who, in 1929, had shut down the Black Chamber: Secretary of War Henry L. Stimson.

However, Hoover’s new Secretary of State did not view the achievements of the Black Chamber in the 1920s with respect or admiration. On the contrary, the idealistic young cabinet secretary immediately withdrew funding for the Black Chamber, and terminated the entire staff, including Herbert Yardley, unfortunately not demanding security or confidentiality agreements from them on their way out the door. Of his handling of the Black Chamber and its staff, the secretary was supposed to have famously said, “Gentlemen do not read each other’s mail.” However, the story of the Black Chamber did not stop there.

Nearly destitute, Yardley proceeded to write his memoirs of the affair, The American Black Chamber. The book was serialized in the pages of The Saturday Evening Post, and rapidly became a runaway international bestseller, chronicling in devastating detail the operations and achievements of the Black Chamber during their decade of operations. Across the globe, governments immediately tightened up their diplomatic protocols and began to systematically improve communications security. This included the development of cipher machines utilizing telephone rotary switches based upon large number theory protocols, such as the German Enigma and Japanese PURPLE. By the outbreak of World War II, virtually every nation in the world was using such machines to protect their diplomatic and military communications, resulting in huge new intelligence enterprises like ULTRA and MAGIC.

Ironically, the Washington, D.C., bureaucrat that eventually authorized the funding and personnel to create MAGIC was the same idealistic gentleman who, in 1929, had shut down the Black Chamber: Secretary of War Henry L. Stimson. A decade of experience watching the rise of fascism across the globe had made Stimson a much wiser and more mature judge of “what gentlemen do” than he had been in 1929. Sadly, however, the amazing resource that had been the Black Chamber, including the incomparable Herbert Yardley and his staff, were lost to America during the critical 1930s, where they might have done valuable work in a world rapidly spinning into madness. And for Stimson, the Black Chamber affair provided an important object lesson in what is possible in the safety of peacetime, as opposed to what is necessary in time of crisis or war.