Much of the movement's history has been shrouded in mystery, largely because successive purges, especially during the Democratic Kampuchea period, have left so few survivors to recount their experiences. One thing is evident, however, the tension between Khmer and Vietnamese was a major theme in the movement's development. In the three decades between the end of World War II and the Khmer Rouge victory, the appeal of communism to Western educated intellectuals (and to a lesser extent its more inchoate attraction for poor peasants) was tempered by the apprehension that the much stronger Vietnamese movement was using communism as an ideological rationale for dominating the Khmer. The analogy between the Vietnamese communists and the Nguyễn Dynasty, which had legitimized its encroachments in the 19th century in terms of the "civilizing mission" of Confucianism, was persuasive. Thus, the new brand of indigenous communism that emerged after 1960 combined nationalist and revolutionary appeals and, when it could afford to, exploited the virulent anti-Vietnamese sentiments of the Khmers. Khmer Rouge literature in the 1970s frequently referred to the Vietnamese as yuon (barbarian), a term dating from the Angkorian period.