Rudy Baker became head of the CPUSA's underground secret apparatus in 1938 succeeding J. Peters. Baker was born in 1898 in Vukovar, Croatia, probably under the name Rudolph Blum. Baker immigrated to the United States with his family in 1909. Baker had little formal education.
Baker shows up in Venona project traffic only under the cover name "Son"; he may also be "Rudi". The identification comes from coded correspondence between the Comintern and the CPUSA in Russia's RTsKhIDNI archive (495-184), which contains dozens of messages from Brother in Moscow to Father and Son in the United States. Annotations on these messages identify Brother as Dimitrov and Father as CPUSA General Secretary Earl Browder. In these messages Son is the head of the CPUSA's covert arm, which Baker took over in mid 1938 after Whittaker Chambers defection. None of the Comintern messages to Son were sent until after Baker visited Moscow in January 1939 to brief Commintern officials on the status of the CPUSA secret apparatus after Baker took over. In May 1942 General Pavel Fitin, the head of KGB foreign intelligence directorate states in a message to Dimitrov found in the Comintern Archives, "We are forwarding a telegram we received from New York addressed to you from Rudy," and the telegram is signed "Son".
The Marxist Internet Archive has unearthed these pseudonyms used by Baker: Baker, Raymond—Baker, Rudy / Bower / Bark / Blum / Rudolph / Taylor, John.
- John Earl Haynes and Harvey Klehr, Venona: Decoding Soviet Espionage in America (New Haven: Yale University Press, 1999).