Felfe rose quickly through the ranks of the West German intelligence service. After his arrest in November 1961 it would be established that as a double agent his over-riding loyalty was to Soviet intelligence, but along the way the Soviet KGB and GRU (Main Intelligence Directorate / Главное разведывательное управление) were keen to preserve his cover and therefore enabled him to provide plenty of credible intelligence to his West German handlers. Subsequently declassified CIA analysis outlines four elaborate operations undertaken in the early 1950s by Soviet Intelligence, under the codes names "Balthasar", "Lena", "Lilli Marlen" and
