CPK members were expected to attend regular (sometimes daily) "lifestyle meetings" in which they engaged in criticism and self-criticism. These cultivated an atmosphere of perpetual vigilance and suspicion within the movement. Pol Pot and Nuon Chea led such sessions at their headquarters, although they were exempt from criticism themselves. By early 1972, relations between the Khmer Rouge and its Vietnamese Marxist allies were becoming strained and some violent clashes had broken out. That year, the North Vietnamese and Viet Cong main-force divisions began pulling out of Cambodia, primarily because they were needed for the offensive against Saigon. As it became more dominant, the CPK imposed increasing numbers of controls over Vietnamese troops active in Cambodia. In 1972, Pol Pot suggested that Sihanouk leave Beijing and tour the areas of Cambodia under CPK control. When Sihanouk did so, he met with senior CPK figures, including Pol Pot, although the latter's identity was concealed from the king.