American POWs were reportedly brainwashed by their Korean and Chinese captors during the Korean War. They were put through extreme conditions, including torture, and their bodies were weakened from malnutrition and sleep deprivation. Several prisoners were not able to handle to strain and confessed to waging germ warfare, even though they did not.

At the end of the war, there were at least 21 POWs who refused to return to the United States when they were freed, pledging allegiance to communism (although it was never ascertained whether they refused to come home due to shame or a real commitment to communism).