Scholars would now be able to learn the secrets of the massive Soviet espionage network which had been active for decades inside the United States.
The narrative of the international communist conspiracy, and how it infiltrated various social institutions and government agencies, would be pieced together with data from a wide variety of sources.
Information became declassified from various Soviet intelligence agencies, like the KGB, once the Soviet Union ceased to exist. Private collections of papers from various former Soviet agents also became public.
Other sources included surveillance files from the FBI, and data from the U.S. Army’s Venona project. In late 1946, officers were able to break secret Soviet codes. Venona, begun in 1943, revealed extensive communist infiltration into various government offices.
Reviewing these various sources of Cold War data for researchers, historians Stan Evans and Herb Romerstein write:
To all of which there should be added — though this too is much neglected — a sizable trove of information about Red activity in the United States collected by committees of the Congress, based on the testimony of ex-Communist witnesses, the findings of staff investigators, and information from intelligence agencies, security squads at the State Department, and other official bodies. Like the endeavors of the FBI, the work of the committees was often downgraded or ignored while the Cold War was in progress. As may be seen today in the light of the new disclosures, the hearings and reports of the House Committee on Un-American Activities, Senate Internal Security Subcommittee, and other panels of the Congress were (and are) a gold mine of useful information on Cold War issues.
Taken together, the bits of information formed a verifiable idea of the Soviet espionage network inside the United States. The first Venona decrypts revealed that communist spies had infiltrated the Manhattan Project and the facilities at Los Alamos, New Mexico.
Spies were also shown to be in several different offices within the federal government, including the State Department and the Treasury Department.
In total, Soviet infiltration and subversion inside the United States was more extensive than scholars had previously suspected.