Unit Oka 9420 was the central
Epidemic Prevention and Water Purification Department
The Epidemic Prevention and Water Purification Department was a department of the Imperial Japanese Army from 1936 to the dissolution of the Army in 1945. While its public mission was to prevent the spread of disease and monitor water supply, sever ...
of the
Southern Expeditionary Army Group
''Nanpō gun''
, image = 1938 terauchi hisaichi.jpg
, image_size = 200px
, caption = Japanese General Count Terauchi Hisaichi, right, commanding officer of the Southern Expedition ...
of the
Imperial Japanese Army
The was the official ground-based armed force of the Empire of Japan from 1868 to 1945. It was controlled by the Imperial Japanese Army General Staff Office and the Ministry of the Army, both of which were nominally subordinate to the Emperor o ...
. Formed in 1942 to support the
Japanese Southern Army, Unit 9420 consisted of two units; the Umeoka Unit, which specialized in the
plague
Plague or The Plague may refer to:
Agriculture, fauna, and medicine
*Plague (disease), a disease caused by ''Yersinia pestis''
* An epidemic of infectious disease (medical or agricultural)
* A pandemic caused by such a disease
* A swarm of pes ...
, and the Kono Unit, which specialized in
malaria
Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
. Most of its work involved preventing the spread of disease in Singapore.
Commanded by Major General
Kitagawa Masataka, the unit was headquartered in the Permai Hospital in Tampoi,
Johor
Johor (; ), also spelled as Johore, is a States and federal territories of Malaysia, state of Malaysia in the south of the Malay Peninsula. Johor has land borders with the Malaysian states of Pahang to the north and Malacca and Negeri Sembilan ...
, near the southern tip of the
Malay Peninsula
The Malay Peninsula (Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The area ...
, 13 km northeast of
Johor Bahru
Johor Bahru (), colloquially referred to as JB, is the capital city of the state of Johor, Malaysia. It is located at the southern end of Peninsular Malaysia,along the north bank of the Straits of Johor, opposite of the city-state Singapore. T ...
and
Singapore
Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...
, with some evidence that it also had sub-units operating in Thailand and working on unknown diseases. Coupled with its work on the plague, the unit was also responsible for rat catching.
According to the testimony of politician
Othman Wok
Othman bin Wok ( Jawi: عثمان بن ووك; b. 8 October 1924 – d. 17 April 2017), often known as Othman Wok, was a Singaporean politician who served as Minister of Social Affairs between 1963 and 1977. After retiring from politics, he wa ...
, Singapore was also an important
biological weapon
A biological agent (also called bio-agent, biological threat agent, biological warfare agent, biological weapon, or bioweapon) is a bacterium, virus, protozoan, parasite, fungus, or toxin that can be used purposefully as a weapon in bioterroris ...
s (BW) base. A laboratory was established there within days of the Japanese conquest. It became one of the largest of the BW installations outside of mainland China. Initially, Unit 9420 was under the command of
Hareyama Yoshio, but in 1942, Lieutenant Colonel
Naito Ryoichi, one of Ishii's most trusted colleagues, assumed control of the facility for several years. It was staffed with approximately 150 physicians and scientists, and produced huge quantities of
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
s annually. Naito and his staff worked primarily with
typhus
Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure.
...
, plague, and
pesticide
Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...
s. It is unknown whether Singapore was a BW research facility, or whether it was simply a laboratory employed to produce pathogens for use elsewhere.
[Sidu H. ''The Bamboo Fortress: True Singapore War Stories''. Singapore: Native Publications; 1991; also printed in ]Straits Times
''The Straits Times'' is an English-language daily broadsheet newspaper based in Singapore and currently owned by SPH Media Trust (previously Singapore Press Holdings). ''The Sunday Times'' is its Sunday edition. The newspaper was establishe ...
, 19 September 1991
References
Japanese biological weapons program
Imperial Japanese Army
Japanese human subject research
History of Singapore
Japanese war crimes
{{Japan-mil-hist-stub