The ideological conflict between the United States and communist Soviet Union known as the Cold War officially went “hot” on June 25, 1950, when tanks and troops of the communist North Korean army crossed the 38th parallel and invaded democratic South Korea. North Korea’s leader, Kim Il Sung, dreamt of uniting all of Korea under his banner; and he almost succeeded. But U.N. troops, led by General of the Army Douglas MacArthur, successfully stopped the North Korean advance at the Pusan Perimeter and then routed the communists with the dramatic amphibious landing at Inchon. After MacArthur ordered his troops north, it appeared that Korea would become a united country – but under South Korean rule. But that dream also was shattered when, on Oct. 19, 1950, the first contingent of more than a million troops of the “Chinese People’s Volunteers” – in reality the Chinese Communist People’s Liberation Army – crossed the Chinese/North Korean border of the Yalu River. This force brought two things into North Korea. The first was 260,000 troops to help North Korea fight the United Nations troops. The second was contagious diseases.

News of the first became brutally evident in November 1950, when the Chinese troops attacked the outnumbered American and South Korean units and forced a long retreat out of North Korea that did not end until those troops stabilized a defensive line south of Seoul, the South Korean capital. But news of deadly contagious disease outbreaks did not reach MacArthur’s headquarters until January 1951.

When the allied troops recaptured Seoul and advanced to the 38th parallel, they discovered a civilian population decimated by epidemics of typhus, smallpox, and typhoid. In addition, thousands of captured Chinese and North Korean troops were found to be ill with these and other contagious diseases.

As it was preparing a counteroffensive to drive the communists completely out of South Korea, CIA-controlled agents operating behind enemy lines began sending reports of disease epidemics among the military and civilian populations in the communist controlled territory.

When the allied troops recaptured Seoul and advanced to the 38th parallel, they discovered a civilian population decimated by epidemics of typhus, smallpox, and typhoid. In addition, thousands of captured Chinese and North Korean troops were found to be ill with these and other contagious diseases. Reports quickly made their way to MacArthur’s top medical officer, Chief of the Public Health and Welfare Section of Supreme Command Allied Powers (SCAP) Brig. Gen. Crawford F. Sams. Some reports indicated that entire villages were wiped out by disease. He also received transcripts of prisoner debriefings. In a 1979 interview, Sams recalled that the POWs stated such things as, “Half my unit’s sick. [Men] turned black when they were dying.” Mentions of victims turning black shortly before their death particularly worried him. It suggested that bubonic plague – “the Black Death” – was in Korea.

When the United Nations troops entered the Korean theater of operations, they were vaccinated for a variety of diseases they were expected to encounter. The one exception was bubonic plague. Bubonic plague vaccines then available conferred immunity for only a short duration. As a result, vaccinations for the disease were conducted on an as-needed basis. Because the plague threatened both the United Nations troops and approximately 23 million civilians in South Korea and it would take time to produce sufficient vaccine to inoculate everyone, confirming the presence of bubonic plague became a top priority.

In February, as news of the epidemic outbreaks became generally known, the North Koreans and Chinese Communists launched an aggressive propaganda campaign regarding them. According to Peking Radio and the People’s Daily, the United Nations forces were conducting biological warfare – dropping canisters filled with insects carrying cholera and other diseases and that germ bombs and artillery shells were being used to infect civilians and troops with smallpox and plague. Kim Il Sung demanded that U.N. commanders Gen. Matthew B. Ridgway and MacArthur be tried for this crime against humanity and he issued an emergency decree calling for the National Extraordinary Anti-Epidemic Committee and other bureaucracies to destroy the insects. At the same time, the communist authorities refused requests to allow independent health inspectors from the International Red Cross and other humanitarian organizations into the infected areas.

MacArthur and his commanders knew the charges that they were conducting biological warfare were false. The truth was that North Korea’s rudimentary healthcare system had collapsed under the combined weight of thousands of infected troops spread throughout the country, a large displaced population, contaminated water, unhygienic living conditions, and other problems. Before he could refute the charges, MacArthur needed proof – an unimpeachable firsthand report from the most senior medical authority possessing experience in dealing with bubonic plague. Only one man in the entire theater fit those criteria: Sams.