Allegations of biological warfare in the Korean War Allegations that the United States military used biological weapons in the Korean War ( 1950 – 53 ) were raised by the governments of People ' s Republic of China , the Soviet Union and North Korea in 1952 . The story was covered by the worldwide press and led to a highly pubicised international investigation . US Secretary of State Dean Acheson and other US and allied government officials denounced the allegations as a hoax . For many years , the allegations continued to have a number of prominent supporters . In 1998 , however , a large cache of Soviet , Chinese and North Korean documents were released indicating that the allegations were part of an elaborate disinformation campaign . Allegations . During 1951 the Communists made vague allegations of biological warfare , but these were not pursued . On 28 January 1952 , the Chinese People ' s Volunteer Army headquarters received a report of a smallpox outbreak southeast of Incheon . From February to March 1952 , more bulletins reported disease outbreaks in the area of Chorwon , Pyongyang , Kimhwa and even Manchuria . The Chinese soon became concerned when 13 Korean and 16 Chinese soldiers contracted cholera and the , while another 44 recently deceased were tested positive for meningitis . Although the Chinese and the North Koreans did not know exactly how the soldiers contracted the diseases , the suspicions soon shifted to the Americans . On 22 February 1952 , the North Korean Foreign Ministry made a formal allegation that American planes had been dropping infected insects onto North Korea . This was immediately denied by the US government . The accusation was supported by Australian reporter Wilfred Burchett , and by the apparent confessions of captured US airmen . The Communists also alleged that US Brigadier General Crawford Sams had carried out a secret mission behind their lines at Wonsan in 1951 , testing biological weapons . He said , however , that he had actually been investigating an outbreak of bubonic plague . When the International Red Cross and the World Health Organization ruled out biological warfare , the Chinese government denounced this as Western bias and arranged an investigation by the World Peace Council . The World Peace Council set up the International Scientific Commission for the Facts Concerning Bacterial Warfare in China and Korea . This commission included several distinguished scientists , including renowned British biochemist and sinologist Joseph Needham . The commission ' s findings also included eyewitnesses , and testimony from doctors as well as four American Korean War prisoners who confirmed the US use of BW . Its final report , which made on 15 September 1952 , was that the allegation was true , that the US was indeed experimenting with biological weapons . The International Association of Democratic Lawyers ( IADL ) also publicized these claims in its 1952 " Report on U . S . Crimes in Korea " , along with journalist John W . Powell . Counterclaims . The US and its allies responded by describing the allegation as a hoax . The US government also declared IADL as a Communist front organization since 1950 , and charged Powell with sedition . Upon release the prisoners of war repudiated their confessions which they said had been extracted by torture . An Australian colleague , Denis Warner , went so far as to suggest that the story had been concocted by Wilfred Burchett as part of his alleged role as a KGB agent of influence . Warner pointed out the similarity of the allegations to a science fiction story by Jack London , a favorite author of Burchett ' s . Based on declassified Russian documents that showed KGB payment to agent Burchett , historians Herbert Romerstein and Robert Manne also believed that Burchett worked for KGB . However , the notion that Burchett originated the " hoax " has been decisively refuted by one of his most trenchant critics , Tibor Méray . Méray worked as a correspondent for Communist Hungary during the war but fled the country after the abortive uprising of 1956 . Now a staunch anti - Communist , he has confirmed that he saw clusters of flies crawling on ice . Méray has argued the evidence was the result of an elaborate conspiracy : " Now somehow or other these flies must have been brought there . . . the work must have been carried out by a large network covering the whole of North Korea . " Disease prevention measures . Recent research has indicated that , regardless of the accuracy of the allegations , the Chinese acted as if they were true . After learning the outbreaks , Mao Zedong immediately requested Soviet assistance on disease preventions , while the Chinese People ' s Liberation Army General Logistics Department was mobilized for anti - bacteriological warfare . On the Korean battlefield , four anti - bacteriological warfare research centers were soon set up , while about 5 . 8 million doses of vaccine and 200 , 000 gas masks were delivered to the front . Within China , 66 quarantine stations were also set up along the Chinese borders , while about 5 million Chinese in Manchuria were inoculated . The Chinese government also initiated the " Patriotic Health and Epidemic Prevention Campaign " and directed every citizen to kill flies , mosquitoes and fleas . These disease prevention measures soon resulted in an improvement of health for Communist soldiers on the Korean battlefield . Tibor Méray provided eyewitness account of North Korean conducting an " unprecedented campaign of public health " during the allegation . Subsequent evaluation . Subsequent historians have offered other explanations to the disease outbreaks during the spring of 1952 . For example , it has been noted that spring time is usually a period of epidemics within China and North Korea , and years of warfare had also caused a breakdown in the Korean health care system . Historians have argued that under these circumstances , diseases could easily spread throughout the entire military and civilian populations within Korea . In 1986 , however , Australian historian Gavan McCormack argued that the claim of US BW use was " far from inherently implausible " , pointing out that one of the POWs who confessed , Colonel Walker Mahurin , was in fact associated with Fort Detrick in Maryland , a biological weapons research facility . A 1988 book on the Korean War , by Western historians Jon Halliday and Bruce Cumings also suggested the claims might be true . The official Chinese government stance by the mid - 1990s was that biological warfare was a real threat at the time and they reacted properly in order to prevent serious epidemics from spreading throughout North Korea and China . In 1998 , Stephen Endicott and Edward Hagermann claimed that the accusations were true in their book , " The United States and Biological Warfare : Secrets from the Early Cold War and Korea " . The book received mixed reviews , some called it " bad history " and " appalling " , while other praised the case the authors made . In response , Kathryn Weathersby and Milton Leitenberg of the Cold War International History Project at the Woodrow Wilson Center released a cache of Soviet and Chinese documents in 1998 showing the North Korean claim to have been an elaborate disinformation campaign . They revealed that North Korea ' s health minister travelled in 1952 to the remote Manchurian city of Mukden where he procured a culture of plague bacilli which was used to infect condemned criminals as part of an elaborate disinformation scheme . Tissue samples were then used to fool the international investigators . The papers included telegrams and reports of meetings among Soviet and Chinese leaders , including Chairman Mao Zedong . A report to Lavrenti Beria , head of Soviet intelligence , for example , stated : " False plague regions were created , burials . . . were organized , measures were taken to receive the plague and cholera bacillus . " These documents revealed that only after Stalin ' s death the following year did the Soviet Union halt the disinformation campaign . Weathersby and Leitenberg consider their evidence to be conclusive — that the allegations were disinformation and no BW use occurred — and their conclusions have been generally accepted . In 2001 , KGB expert Herbert Romerstein also criticized Endicott ' s research on the basis that it is purely based on accounts provided by the Chinese government . Author Simon Winchester concluded in 2008 that the KGB was sceptical of the allegation , but that North Korea leader Kim Il Sung believed it . Winchester believed the question " has still not been satisfactorily answered " .