This unit extensively and secretly researched biological warfare and other subjects through human experimentation during the Second Sino-Japanese War from 1938 to 1945.

It entered Guangzhou in late October and took the campus of the National Sun Yat-sen University School of Medicine as its headquarters.

[3]: 223 The headquarters of Unit 8604 had a General Affairs Division, responsible for logistics, personnel and financial management.

In the basement of the fourth class's building, many formalin-soaked corpses were stored, and the chief of the section performed autopsies every day.

[3]: 21 The unit engaged in bacteriological research, normally breeding 10,000 rats per month and producing 10 kilograms of plague fleas.

Local residents had observed Japanese soldiers collecting rats with military vehicles and transporting them in carloads to Unit 8604.