 Meanwhile, the Khmer Rouge purged Kampuchea of internal enemies (social class and political, cultural and ethnic) at the Killing Fields, the scope of which became crimes against humanity for the deaths of 2,700,000 people by mass murder and genocide.That social restructuring of Cambodia into Kampuchea included attacks against the Vietnamese ethnic minority of the country which aggravated the historical, ethnic rivalries between the Viet and the Khmer peoples.Beginning in September 1977, Kampuchea and the Socialist Republic of Vietnam continually engaged in border clashes.