there were 200,000. In addition to being a proscribed ethnic group by the government, the Chinese were predominantly city-dwellers, making them vulnerable to the Khmer Rouge's revolutionary ruralism. The government of the People's Republic of China did not protest the killings of ethnic Chinese in Cambodia. The policies of the Khmer Rouge towards Sino-Cambodians seems puzzling in light of the fact that the two most powerful people in the regime and presumably the originators of the racist doctrine, Pol Pot and Nuon Chea, both had mixed Chinese-Cambodian ancestry. Other senior figures in the Khmer Rouge state apparatus such as Son Sen and Ta Mok also had Chinese ethnic heritage. In the late 1980s, little was known of Khmer Rouge policies toward the tribal peoples of the northeast, the Khmer Loeu. Pol Pot established an insurgent base in the tribal areas of Ratanakiri Province in the early 1960s, and he may have had a substantial Khmer Loeu following. Predominantly animist peoples, with few ties to the Buddhist culture of the lowland Khmers, the Khmer Loeu had resented Sihanouk's attempts to "civilise" them. There were also high rates of sexual violence during the regime. Terror A security apparatus called Santebal was part of the Khmer Rouge organizational structure well before 17 April 1975, when the Khmer Rouge took control over Cambodia. Son Sen, later the Deputy Prime Minister for Defense of Democratic Kampuchea, was in charge of the Santebal, and in that capacity he appointed Kang Kek lew (Comrade Duch) to run its security apparatus. When the Khmer Rouge took power in 1975, Duch moved his headquarters to Phnom Penh and reported directly to Son Sen. At that time, a small chapel in the capital was used to incarcerate the regime's prisoners, who totaled fewer than two hundred. In May 1976, Duch moved his headquarters to its final location, a former high school known as Tuol Sleng, which could hold up to 1,500 prisoners. The Khmer Rouge government arrested, tortured, and eventually executed anyone suspected of belonging to several categories of supposed "enemies": Anyone with connections to the former government or with foreign governments. Professionals and intellectuals—in practice this included almost everyone with an education, people who understood a foreign language, and even people who required glasses. However, ironically, Pol Pot himself was a university-educated man (albeit a drop-out) with a taste for French literature and was also a fluent French speaker.