The Ningbo plague attack () was a secret biological warfare attack launched by Japan in October 1940 against the Kaiming Street area of Ningbo, Zhejiang, China, using fleas infested with plague (Yersinia pestis). A joint operation of the Imperial Japanese Army's Unit 731 and Unit Ei 1644, which airdropped wheat, corn, cotton scraps, and sand infected with plague fleas to target locations.
After the outbreak of the plague, the city authorities in Ningbo built an isolation wall high around the epidemic area, segregating patients and suspected cases, and eventually burned down the Kaiming Street area to eradicate the disease. Until the 1960s, this burned area was still referred to as the "plague field". According to the doctoral thesis of Junichi Kaneko, a military doctor of Unit 731, on October 27, 1940, Unit 731 spread of plague bacteria over Ningbo using aircraft, resulting in a total of 1,554 deaths from the first- and second-round infections.
Background
Japanese biological warfare plan
In June 1925, Japan signed the Geneva Protocol, which committed Japan to refrain from using biological and chemical weapons in warfare. The development of Japan's biological weapons was highly secretive and led by Shiro Ishii. He planned and raised funds for Japan's biological weapons program. In 1939, the Imperial Japanese Army established Unit Ei 1644 in Nanjing to conduct research on biological and chemical weapons. Units Ei 1644 and 731 studied the effects of various chemicals and pathogens that could be used as biological weapons on soldiers and civilians and developed weapons to further expand the Japanese Empire's territory in Asia. On June 13, large quantities of white powder were airdropped in the vicinity of Lihai, Shaoxing. On June 15, chemical tests conducted by the local river police did not reveal any abnormalities, but subsequent bacterial culture tests revealed turbidity in one test tube and cotton-like floating substances in another, with pathogens such as tetanus and diphtheria observed under a microscope. Within days after the airdrop, the weather in Shaoxing was clear and sunny, with abundant sunlight, which was not conducive to bacterial growth, so no epidemic outbreak occurred. This is the earliest recorded instance of the Japanese military's bacteriological weapon attack in Zhejiang.
Strategic location of Ningbo
Before 1937, Zhejiang cities such as Ningbo, Jinhua, and Quzhou in Zhejiang did not experience a plague epidemic. However, people may have been aware of the plague near Ningbo in Shanghai in 1910. The incubation period of the plague is 2 to 8 days. At the time of the outbreak, sulfa drugs, streptomycin, and other antibiotics had not yet been invented, so residents of Ningbo could not have access to antibiotics and were primarily treated with serum. Without treatment, the mortality rate of the plague was almost 100%, and there was not enough serum supply prepared in advance.
Since the first Japanese air raid on Lishe Airport on August 16, 1937, the Japanese military had directly attacked Ningbo at least 7 times. On 17 July 1940, the Japanese military first invaded Zhenhai, but were driven out by the Chinese army five days later on the 22nd. The Japanese military again bombed Ningbo on 5 and 10 September of the same year. From 18 September to 8 October, the Japanese launched a total of six attacks on Ningbo, none of which resulted in a plague outbreak. Despite fleas being dropped in Quzhou on 4 October, there were no apparent effects by the end of October. The airstrikes in Quzhou did not attract the attention of the provincial government, which instead focused on a plague outbreak in Qiyuan, not associated with the Imperial Japanese Army. People noticed a sudden increase in fleas in Donghou Street and Kaiming Street, but there were no reports of mass deaths in rodents. Rumours circulated that the Japanese air raid was actually a biological weapons attack. Subsequently, people from neighbouring establishments such as Wang Shunxing's bakery, Hu Yuanxing's dominoes shop, Yuan Tai Hotel, Bao Changxiang underwear shop on East Zhongshan Road, and the vicinity of Donghou Street, all experienced fatalities. Initially, people mistook it for bubos or malignant malaria. People sought quinine from hospitals, but it proved ineffective.
To address the issue of handling materials within the epidemic area, a property registration office was established to register all houses and items within the epidemic area. For valuable or movable items, disinfection was mandatory before removal from the epidemic area. Two large stoves were constructed on the open ground of Kaiming Lane in the southwest corner of the epidemic area for boiling and disinfection purposes. Disinfection personnel wore protective clothing and hats, and based on the household information in the registration book, items were removed for disinfection house by house, with family members responsible for collection. Until the 1960s, this burned area was still referred to as the "plague field".
Theory of biological warfare
On 28 November 1940, the Japanese bombed Jinhua, scattering granular particles resembling fish eggs, which were confirmed to contain Yersinia pestis. Chen Wanli and other Zhejiang health officials were disbelieved by the experts of National Health Administration, including Robert Pollitzer. During the Zhejiang Plague Consultation Conference chaired by Jin Baoshan, Robert Pollitzer expressed skepticism about the theory of bacteriological warfare causing the plague.
On 4 November 1941, using the same method, the Japanese attacked Changde, resulting in 2810 being infected with the plague. Immediately after the attack, Chen Wengui led a team to investigate. He performed autopsies on the bodies and injected lymph node puncture blood from patients into guinea pigs, which died five days later. By observing patient samples and conducting pathological analysis, it was concluded that the patients died from sepsis caused by Yersinia pestis. Chen Wengui compiled the evidence gathered into the "Investigation Report on the Plague in Changde, Hunan", confirming Japanese bacteriological warfare. However, the Nationalist government, considering the matter's impact on international credibility, altered the report. It was not until 1950 that the report resurfaced from the archives.
The cover of the report bears the words "Military Secret" and contains the name of a senior military doctor who graduated from Teikyo University and recorded the content on December 14, 1943. The report explains that "PX" refers to fleas infected with Yersinia pestis, and it calculates the effectiveness of spreading bacteria bombs on the battlefield. The report lists the quantities of PX used and the number of infected individuals in various locations in China, including Nong'an, Quzhou, Ningbo, Changde, Guangxin, Guangfeng and Yushan. It states that over 26,000 people were infected once or twice, defining PX as "the best bacterial bomb, capable of causing psychological and economic panic".
Trials
Khabarovsk, Soviet Union
On 25 December 1949, the Soviet Union began the trial of Japanese prisoners of war involved in bacteriological warfare in Khabarovsk. During the Khabarovsk trial, Japanese prisoners admitted to the events of the "aerial dissemination of pathogens" that took place in Ningbo in 1940. Susumu Hatano testified that the experiment in Ningbo was the first actual field test and, because it was conducted on enemy territory, the results were inconclusive. However, the Japanese military drew conclusions about the bacteriological warfare experiment based on information recorded in Ningbo newspapers and laboratory test data. It wasn't until the publication of The Devil's Gluttony in 1981 that the unit's activities were first revealed to the public. In the first half of the 20th century, including during World War II, dozens of lawsuits for wartime compensation were filed against the Japanese government and companies associated with Japanese aggression. However, almost all of these lawsuits were rejected by Japanese courts. Nevertheless, the Japanese government has never formally acknowledged that the Japanese military conducted bacteriological warfare. Despite a series of confessions from former soldiers, the Japanese government acknowledged the unit's existence but still refused to disclose the scope of scientists' activities. During the debates in the Tokyo District Court, Chinese bacteriologist Huang Ketai pointed out that unlike previous epidemics, the Ningbo plague in 1940 occurred in winter rather than summer and was carried by fleas that were not native to the region, killing humans without affecting mice.
In 2002, based on 28 hearings and a large amount of evidence, the Tokyo District Court wrote a written summary confirming for the first time that the Japanese military conducted bacteriological warfare. However, many plaintiffs were angry at the rejection of their compensation claims and appealed.
Memorials
thumb|The Ningbo Plague Memorial Monument
On 3 September 1995, the Ningbo Municipal People's Government erected a monument on the pedestrian walkway of Kaiming Street, inscribed with the words "Site of the Plague Field in Ningbo Infected by the Bacteriological Warfare of the Japanese Invaders", with the central inscription reading "Never Forget National Humiliation, Strive to Strengthen the Nation". It was signed by "Various sectors of Ningbo City on the 50th anniversary of the victory of the War of Resistance Against the Japanese". In 2005, the monument was relocated to the original site of the bacteriological epidemic area on the west side of Tianyi Haoting. The new monument's front is engraved with the words "Do Not Forget National Humiliation, Strive to Strengthen the Nation", with bacteriological warfare historical materials and a list of victims carved on both sides.
In 2009, the Publicity Department of Haishu District Committee, the District Radio, Television, and News Bureau, the District Cultural Relics Management Office, and the Ningbo New Fourth Army Historical Research Association jointly established the "Ningbo Kaiming Street Plague Disaster Exhibition Hall" on the second floor of the Tianyi Business Circle Party and Mass Service Center. The curved wall on the right side of the entrance of the exhibition hall lists the names of all the victims. In the centre of the hall, there is a sand table displaying a model of the buildings in the Kaiming Street epidemic area, reconstructed according to the "Epidemic Area Map" provided by the family of the victim Hu Dingyang.