Korean Armistice Agreement
On 27 July 1953, the Korean Armistice Agreement was signed, launching Operation Big Switch, the repatriation of Korean War POWs. (Ultimately, some 12,773 UN POWs were repatriated.) Twenty-one American POWs refused repatriation and defected, and the returning POWs were viewed as potential security risks. As a result, debriefings became "hostile investigations in search of possible disloyalty".