Surgeon General Shirō Ishii was a Japanese war criminal, microbiologist and army medical officer who was the director of Unit 731, a biological warfare unit of the Imperial Japanese Army. Ishii led the development and application of biological weapons at Unit 731 in Manchukuo during the Second Sino-Japanese War from 1937 to 1945, including the bubonic plague attacks at Chinese cities of Changde and Ningbo, and planned the Operation Cherry Blossoms at Night biological attack against the United States.

Beginning in the mid-1930s, Japan conducted numerous attempts to acquire and develop weapons of mass destruction. The 1943 Battle of Changde saw Japanese use of both bioweapons and chemical weapons, and the Japanese conducted a serious, though futile, nuclear weapon program.