North Vietnam and were considered too sympathetic to them. Most of these people were later executed. In summer 1973, the Khmer Rouge launched its first major assault on Phnom Penh, but was forced back amid heavy losses. Later that year, it began bombarding the city with artillery. In the autumn, Pol Pot traveled to a base at Chrok Sdêch on the eastern foothills of the Cardamom Mountains. By winter, he was back at the Chinit Riber base where he conferred with Sary and Chea. He concluded that the Khmer Rouge should start talking openly about its commitment to making Cambodia a socialist society and launch a secret campaign to oppose Sihanouk's influence. In September 1974, a Central Committee meeting was held at Meakk in Prek Kok commune. There the Khmer Rouge agreed that it would expel the populations of Cambodia's cities to rural villages. They thought this was necessary to dismantle capitalism which they associated with the urban culture. By 1974, Lon Nol's government had lost a great deal of support, both domestically and internationally. In 1975, the troops defending Phnom Penh began discussing surrender, eventually doing so and allowing the Khmer Rouge to enter the city on 17 April. There, Khmer Rouge soldiers executed between 700 and 800 senior government, military, and police figures. Other senior figures escaped; Lon Nol fled into exile in the US. He left Saukham Khoy as acting president, although he too fled aboard a departing US Navy ship just twelve days later. Within the city, Khmer Rouge militia under the control of different Zone commanders clashed with one another, partly as a result of turf wars and partly due to the difficulty of establishing who was a group member and who was not. The Khmer Rouge had long viewed Phnom Penh's population with mistrust, particularly as the city's numbers had been swelled by peasant refugees who had fled the Khmer Rouge's advance and were considered to be traitors. Shortly after taking the city, the Khmer Rouge announced that its inhabitants had to evacuate to escape a forthcoming US bombing raid; the group falsely claimed that the population would be allowed to return after three days. This evacuation entailed moving over 2.5 million people out of the city with very little preparation; between 15,000 and 20,000 of these were removed from the city's hospitals and forced to march. Checkpoints were erected along the roads out