Video reveals operation of Unit 731 branch in Singapore during WWII

Video footage, shot by a Japanese officer who had been dispatched to Singapore from 1942 to 1943 to supervise the work of the OKA 9420, shows the Japanese army's biological warfare branch during World War II in Singapore.

Japanese personnel wearing white laboratory coats were seen working at the local college of medicine building in the Outram Park in Central Singapore.

Japanese researcher Fuyoko Nishisato, who wrote the book "Behind Bayonets and Barbed Wire: the Secrets of Japanese Army Unit 731", found and made the video public with the help of the Singaporean history buff Lim Shao Bin.

While investigating his grandfather's death in the war, Lim also uncovered other documents on OKA 9420. Among them is a 200-page medical publication and a wartime staff register.

Dated December 1942 to August 1943, the Southern Army Epidemic Prevention and Water Supply Department Research Report, Volume C, appears to be the first written evidence on the diseases the OKA 9420 was studying.

The wartime register shows OKA 9420 started with 146 Japanese staff members in May 1942. By Jan 1, 1945, its operations in Singapore and the region had grown to 862. Among them were doctors, virus specialists and nurses.

National University of Singapore professor Brian Farrell said: "These documents suggest the Japanese army institution's focus on biological warfare is perhaps more widespread than we have been led to believe through Japanese accounts."