The Soviet Union’s approach to biological warfare took a new turn in September 1945, Ken Alibek explains (in Biohazard), when Soviet troops in Manchuria overran a Japanese military facility known as Water Purification Unit 731:
The unit, commanded by Lieutenant General Shiro Ishii, experimented with anthrax, dysentery, cholera, and plague on U.S., British, and Commonwealth POWs. During the Japanese invasion of Manchuria, porcelain canisters of fleas infected with plague and other primitive biological weapons were used in air raids that killed thousands of rural Chinese.
The captured Japanese documents were sent to Moscow, where they made absorbing reading. They included blueprints for biological warfare assembly plants, far larger and more complex than our own. Japan’s program had been organized like a small industry, with a central production facility fed by continuous research and development.
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In 1946, a year after the war ended, a new army biological research complex was established at Sverdlovsk.