"In April–May 1970, many North Vietnamese forces entered Cambodia in response to the call for help addressed to Vietnam not by Pol Pot, but by his deputy Nuon Chea. Nguyen Co Thach recalls: "Nuon Chea has asked for help and we have liberated five provinces of Cambodia in ten days." In 1970, in fact, Vietnamese forces occupied almost a quarter of the territory of Cambodia, and the zone of communist control grew several times, as power in the so-called liberated regions was given to the CPK [Khmer Rouge]. At that time relations between Pol Pot and the North Vietnamese leaders were especially warm." The North Vietnamese trusted Nuon Chea more than Pol Pot or Ieng Sary, although Chea "consistently and consciously deceived the Vietnamese principals concerning the real plans of the Khmer leadership." As a result, "Hanoi did not undertake any action to change the power pattern within the top ranks of the Communist Party to their own benefit." Career As the recently proclaimed state legislature, the Kampuchean People's Representative Assembly held its first plenary session during 11–13 April 1976, Chea was elected president of its Standing Committee. He briefly held office as acting prime minister when Pol Pot resigned for one month, citing health reasons. According to Dmitry Mosyakov, "In October 1978, Hanoi still believed that 'there were two prominent party figures in Phnom Penh who sympathized with Vietnam—Nuon Chea and the former first secretary of the Eastern Zone, So Phim. Vietnamese hopes that these figures would head an uprising against Pol Pot turned out to be groundless: So Phim perished during the revolt in June 1978, while Nuon Chea, as it is known, turned out to be one of the most devoted followers of Pol Pot—he did not defect to the Vietnamese side....It is difficult to understand why until the end of 1978 it was believed in Hanoi that Nuon Chea was 'their man' in spite of the fact that all previous experience should have proved quite the contrary. Was Hanoi unaware of his permanent siding with Pol Pot, his demands that 'the Vietnamese minority should not be allowed to reside in Kampuchea', his extreme cruelty, as well as of the fact that, 'in comparison with Nuon Chea, people considered Pol Pot a paragon of kindness'?" Nuon Chea was forced to abandon his position as president of the Assembly, along with all others as the Vietnamese captured Phnom