Although the Federal Bureau of Investigation was slow to appreciate the scale of the overlap between Soviet-inspired espionage and the CPUSA, intensive surveillance and the recruitment of sources within the party established a pattern of activists, members, and fellow travelers being approached to undertake clandestine duties on behalf of the NKVD. Moscow’s exploitation of the party became apparent in the 1930s when the CPUSA’s general secretary, Earl Browder, was himself directly implicated in the work of the underground cells. He went on a mission to China on behalf of the party, and both his sister Margaret and his common-law wife Kitty Harris operated in Europe as illegals. VENONA intercepts proved that Browder was anxious that he could be compromised by the illicit activities conducted by members of his own family. Simultaneously, the
defections of Whittaker Chambers, Louis Budenz, and Elizabeth Bentley provided the FBI with proof that the CPUSA, which at the height of its popularity achieved a membership of an estimated 75,000, accommodated a massive spy ring.
The FBI’s investigation into atomic espionage revealed that numerous CPUSAactivists had engaged in espionage, and a network run by Julius and Ethel Rosenberg, two CPUSA members in New York, was almost entirely dependent upon his party contacts. Similarly, surveillance on the NKVD rezident, Vasili Zarubin, in 1944 identified his West Coast contact as Steve Nelson, a senior party organizer in California who was engaged in the recruitment of party members and fellow travelers at the Radiation Laboratory in Berkeley and the weapons development facility at Los Alamos National Laboratory.
Once the FBI had established the overlap between the party, volunteers who had fought in Spain with the Abraham Lincoln Battalion of the International Brigade, and Soviet espionage, whole chapters were placed under intensive surveillance, and informants were recruited or planted inside the organization. In addition, an operation code-named TOPLEV was initiated to cultivate sources within the hierarchy, which ultimately resulted in the recruitment of Morris Childs, code-named SOLO. Thereafter the CPUSA was rendered impotent as an instrument of Soviet espionage, with the FBI effectively taking control of some of the party’s activities.
The Smith Act, which in 1948 outlawed any political party’s advocating the violent overthrow of the United States government, enabled the FBI to convict 109 of the CPUSA’s leadership, leaving the organization impotent and of no significance in future Soviet intelligence operations.