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.