 Complete the following phrase:  After taking power and distancing himself from the Vietnamese, pro-China Khmer Rouge leader Pol Pot killed 1.5 to 2 million Cambodians in the killing fields, roughly a quarter of the Cambodian population an event commonly labelled the Cambodian genocide. Martin Shaw described these atrocities as the purest genocide of the Cold War era. Backed by the Kampuchean United Front for National Salvation, an organization of Khmer pro-Soviet Communists and Khmer Rouge defectors led by Heng Samrin, Vietnam invaded Cambodia on 22 December 1978. The invasion succeeded in deposing Pol Pot, but the new state would struggle to gain international recognition beyond the Soviet Bloc sphere. Despite the previous international outcry at the Pol Pot regimes gross human rights violations, representatives of the Khmer Rouge were allowed to be seated in the UN General Assembly, with strong support from China, Western powers, and the member countries of ASEAN. Cambodia would become bogged down in a guerrilla war led from refugee camps located on the border with Thailand. Following the destruction of the Khmer Rouge, the national reconstruction of Cambodia would be severely hampered, and Vietnam would suffer a punitive 