In 1932, chief Japanese medical officer Shirō Ishii was appointed as the coordinator and head of the Army Epidemic Prevention Research Laboratory, also known as AEPRL.
After becoming in charge of the AEPRL, Ishii organized the creation of a covert unit that was tasked with researching biological, bacterial, and chemical warfare: the Tōgō Unit. Ishii was spurred onto the idea based on his visits to other countries' research facilities during the span of 1928, as he was concerned that the Allies might use the newly emerging form of warfare on the Japanese
Ishii was said to have been intrigued with the potential uses of disease in a martial context, but he was reportedly “frustrated by his inability to test his laboratory results on humans."
The Tōgō Unit was Ishii's response to this morbid dissatisfaction, and the unit was established to conduct first-hand experiments on human subjects. The unit was stationed at the Zhongma Fortress experimentation camp, which, after a prison escape and a later explosion, was closed due to fears of discovery by the wider Japanese populace.
Soon after Zhongma's closure in 1935, Ishii was granted permission to create a much larger facility— which would eventually become the infamous Unit 731.