Although unprecedented in scale and ambition, Stalin’s offensive biological warfare program was not an isolated phenomenon. It can instead be viewed as a response to, and extension of, the biological sabotage programs pursued during the First World War by Germany. During the nearly three-decade period of Stalin’s leadership (1924-1953), two distinct, and highly compartmentalized, components of the Soviet Union’s offensive biological warfare program are in evidence. The main strand was launched by the Red Army in Moscow in 1926 and is very well-documented with numerous archival and secondary sources available. There is in addition a second, earlier and much more ephemeral strand, which is based in Leningrad, which was mainly concealed within the RSFSR People’s Commissariat of Health (RSFSR Narkomzdrav) and the Red Army’s Military-Medical Academy.