Col. Boris Bykov

Bykov was allegedly Chambers' boss in the Communist underground, succeeding J. Peters. Chambers said Bykov instructed him to begin collecting documents to be passed on to the Soviet Union.

Chambers' accounts of his relationship with Bykov were amplified over years of retelling. Bykov was not mentioned by Chambers in his 1939 interview with Adolf Berle, according to Berle's notes from the session. In his interview with the FBI in 1942, he said he had only met Bykov in passing. He told a similar story to the FBI in a 1945 interview.

The FBI was never able to establish that Bykov had ever entered the U.S. or that he existed. Julian Wadleigh testified he had met Chambers' boss, who he identified as "Sasha," but that the man had only one arm. Chambers said Bykov had two.