 After the Vietnamese invasion of 1978, the defeat of the Khmer Rouge and the subsequent establishment of the People's Republic of Kampuchea, Sihanouk was asked by the Khmer Rouge leadership to present the case of Democratic Kampuchea at the United Nations.Sihanouk publicly broke with the Khmer Rouge, demanding that they be expelled from the UN as mass murderers.The Khmer Rouge attempt at establishing a new front organization - Patriotic and Democratic Front of the Great National Union of Kampuchea - to re-legitimize their thoroughly discredited 'Democratic Kampuchea' regime met with little success at first.