The intellectual ferment of Paris must have been a dizzying experience for young Khmers fresh from Phnom Penh or the provinces. A number sought refuge in the dogma of orthodox Marxism-Leninism. At some time between 1949 and 1951, Pol Pot and Ieng Sary joined the French Communist Party, the most tightly disciplined and Stalinist of Western Europe's communist movements. The party was also very anti-intellectual. 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. In 1956, however, Hou Yuon and Khieu Samphan helped to establish a new group, the Khmer Students' Union. Inside, the group was still run by the Cercle Marxiste.