was determined to turn the country into a nation of peasants in which the corruption and "parasitism" of city life would be completely uprooted. Communalisation was implemented by putting men, women and children to work in the fields, which disrupted family life. The regime claimed to have "liberated" women through this process and according to Zal Karkaria "appeared to have implemented Engels's doctrine in its purest form: women produced, therefore they had been freed". Under the leadership of Pol Pot, cities were emptied, organised religion was abolished, and private property, money and markets were eliminated. An unprecedented genocide campaign ensued that led to annihilation of about 25% of the country's population, with much of the killing being motivated by Khmer Rouge ideology which urged "disproportionate revenge" against rich and powerful oppressors. Victims included such class enemies as rich capitalists, professionals, intellectuals, police and government employees (including most of Lon Nol's leadership), along with ethnic minorities such as Chinese, Vietnamese, Lao and Cham. The Khmer Rouge regime was one of the most brutal in recorded history, especially considering how briefly it ruled the country. Based on an analysis of mass grave sites, the DC-Cam Mapping Program and Yale University estimated that the Khmer Rouge executed over 1.38 million people. If deaths from disease and starvation are counted, as many as 2.5 million people died as a result of Khmer Rouge rule. This included most of the country's minority populations. For instance, the country's ethnic Vietnamese population was almost completely wiped out; nearly all ethnic Vietnamese who did not flee immediately after the takeover were exterminated. Fall and aftermath Not content with ruling Cambodia, the KR leaders also dreamed of reviving the Angkorian empire of a thousand years earlier, which ruled over large parts of what today are Thailand and Vietnam. This involved launching military attacks into southern Vietnam in which thousands of unarmed villagers were massacred. Immediately following the Khmer Rouge victory in 1975, there were skirmishes between their troops and Vietnamese forces. Many incidents occurred in May 1975. The Cambodians launched attacks on the Vietnamese islands of Phú Quốc and Thổ Chu causing the death of over 500 civilians and intruded into Vietnamese border provinces. In late May, at about the same time that the United States launched an airstrike against the oil refinery at Kompong Som, following the Mayagüez incident, Vietnamese forces seized the Cambodian island of Poulo Wai.