Career
His diplomatic role was a cover for his true activities as an People’s Commissariat of Internal Affairs Senior Case Officer for the Soviet spy network in the United States during the 1940s until his return to the Soviet Union in 1946. Yatskov began work in the central apparatus for external reconnaissance in 1940. In 1941 he was sent to the New York Rezidentura as an operational worker
He carried out critical operations on the acquisition of information on the Manhattan project ("ENORMOZ").
This information allowed Soviet scientists to obtain the highly useful data about the building of facilities for production of weapons-grade uranium and plutonium, and also directly on the production of the atomic bomb. Yatskov collaborated with Harry Gold, who stole industrial formulas from the Pennsylvania Sugar Company, and Soviet Union spy-master Alexander Feklisov in the infiltration of the United States" Manhattan Project by having Gold liaise with scientist Klaus Fuchs.
He also was one of the handlers of Julius Rosenberg and was originally named in the indictment against the Rosenbergs, Morton Sobell and David Greenglass. However, Yakovlev was excluded from the indictment due to diplomatic immunity, and had, in any case, returned to the Union of the Soviet Socialist Republics four years prior to the indictment.
After returning to the Soviet Union, Yatskov continued to work in control of scientific and technical intelligence.
He repeatedly was engaged in operational work in Europe and Asia. Yatskov, in an interview in October 1992, said the Federal Bureau of Investigation uncovered "perhaps less than half" of his network. He referred to Perseus as a code name for a major source still alive.