At some time between 1949 and 1951 , Pol Pot and Ieng Sary joined the French Communist Party . In 1951 , the two men went to East Berlin to participate in a youth festival . This experience is considered to have been a turning point in their ideological development . Meeting with Khmers who were fighting with the Viet Minh ( and whom they subsequently judged to be too subservient to the Vietnamese ) , they became convinced that only a tightly disciplined party organization and a readiness for armed struggle could achieve revolution . They transformed the Khmer Students ' Association ( KSA ) , to which most of the 200 or so Khmer students in Paris belonged , into an organization for nationalist and leftist ideas . Inside the KSA and its successor organizations was a secret organization known as the Cercle Marxiste . The organization was composed of cells of three to six members with most members knowing nothing about the overall structure of the organization . In 1952 , Pol Pot , Hou Yuon , Ieng Sary and other leftists gained notoriety by sending an open letter to Sihanouk calling him the " strangler of infant democracy " . A year later , the French authorities closed down the KSA , but Hou Yuon and Khieu Samphan helped to establish in 1956 a new group , the Khmer Students ' Union . Inside , the group was still run by the Cercle Marxiste
youth festival
3rd World Festival of Youth and Students
Communist Party of Kampuchea