[Japan's Unit 731 remains central to the fiercely contested China-Japan controversy over war crimes and war memory, and to the international debate on science and ethics. With a staff of more than 10,000, including many of Japan's top medical scientists, 731 and its affiliated units conducted human experiments, including vivisection, on Chinese and other victims in Manchukuo and throughout China between 1933 and 1945. The experiments tested, among other things, the lethality of biological weapons and sought to determine the ability of the human body to survive in the face of various pathogens and in conditions such as extreme cold.