Unit 731 was a covert biological and chemical warfare research and development unit of the Imperial Japanese Army that undertook lethal human experimentation during the Second Sino-Japanese War (1937–1945) and World War II. It was responsible for some of the most notorious war crimes carried out by Japanese personnel.
Unit 731 was the code name of an Imperial Japanese Army unit officially known as the Kempeitai Political Department and Epidemic Prevention Research Laboratory. It was initially set up under the Kempeitai military police of the Empire of Japan to develop weapons of mass destruction for potential use against Chinese, and possibly Soviet forces.
Unit 731 was based at the Pingfang district of Harbin, the largest city in the Japanese puppet state of Manchukuo (now Northeast China). More than ten thousand people, from which around 600 every year were provided by the Kempeitai, were subjects of the experimentation conducted by Unit 731.
More than 95 percent of the victims who died in the camp based in Pingfang were Chinese and Korean, including both civilian and military. The remaining 5 percent were South East Asians and Pacific Islanders, at the time colonies of the Empire of Japan, and a small number of the prisoners of war from the Allies of World War II.