Японский отряд по исследованию болезней «Ока» 9420: Деятельность в Юго-Восточной Азии

Disease Research Unit of Japanese Army

Unit Oka 9420 (岡9420部隊), also known as the Epidemic Prevention and Water Purification Department of the Southern Expeditionary Army Group (南方軍防疫供水部), was a disease research unit within the Japanese army. Founded in Nanjing, China in 1942 and headquartered in Japanese occupied Singapore,

In early 1942, the Japanese military established the pioneer team of the Epidemic Prevention and Water Purification Department of the Southern Expeditionary Army Group in Nanjing, China. Following its formation by 26 March, the team left China via Shanghai, Taiwan and Manila and arrived in Singapore by 20 June. The unit was initially given the secret code "Oka" (岡), as this was the secret code for the Seventh Area Army. Following a transfer of control to the Southern Expeditionary Army, the unit also used the secret code for the army, "Joyo" (威). the unit consisted of two teams, including one team, the Umeoka Unit, specialised for studying bubonic plague and the other, the Kono Unit, focusing on malaria. The stated mission of Unit 9420 was ostensibly to address local infectious disease issues, which attracted local elites such as Othman Wok, who was one of the founding father of the Republic of Singapore in the 1960s. As the only biochemical unit established outside of Japan, the all members of the unit came from Nanjing's Unit 1644, but some were directly sent from Japan. From April to June 1943, the unit was temporarily stationed in Thailand to provide services for the construction of the Thai Burma railway before returning to Singapore.

The headquarters of Unit 9420 was established at King Edward VII College of Medicine, with six laboratories inside. According to the research findings of Unit 731, the optimal climatic conditions for breeding fleas were a temperature of 22 degree Celsius and 76% humidity, which was consistent with the climate in Southeast Asia. For every ten thousand rats, ten kilograms of fleas could be produced. Malaya Peninsula thus became the largest flea farm for the Japanese military outside of Japan and China. Researchers fed captured rats, injected them with Yersinia pestis, causing the rats to become sick and produce fleas. The fleas then fed on the dead hosts, and researchers separated them from the host's body, fed them blood, and every three to four months, they sent the fleas in glass bottles to Thailand. On the other side of the laboratory was an isolation wall with a 24 hour operating boiler outside to burn the bodies of rats and provide boiling water for disinfection. According to British military tribunal records, the Japanese military tested a poison named "Ipoh" in the form of live human experiments at the Taiping Prison in Perak.

In Indonesia, Unit 9420 established branches in Jakarta and Bandung.

In northern Burma and western Yunnan, China, the Southern Army Unit 9420 Epidemic Prevention and Water Supply Department was stationed to collect and breed rats and cultivate bacteria. In Papua New Guinea, Unit 9420 established branches in Rabaul and Buin. In the Philippines, Unit 9420 established a branch in Manila. Starting from 4 May 1942, Japanese forces bombed Baoshan, Yunan on the Burma Road with cholera weapons, after they had bombed the town with incendiary munitions since 3 January 1941.