projects. Khmer Rouge era In 1975 when the communist Khmer Rouge took control of Cambodia, they tried to completely destroy Buddhism and very nearly succeeded, when considering this religion as "reactionary". By the time of the Vietnamese invasion in 1979, nearly every monk and religious intellectual had been either murdered or driven into exile, and nearly every temple and Buddhist temple and library had been destroyed. The Khmer Rouge policies towards Buddhism—which included the forced disrobing of monks, the destruction of monasteries, and, ultimately, the execution of uncooperative monks—effectively destroyed Cambodia's Buddhist institutions. Monks who did not flee and avoided execution lived among the laity, sometimes secretly performing Buddhist rituals for the sick or afflicted. Estimates of the number of monks in Cambodia prior to the ascension of the Khmer Rouge vary, ranging between 65,000 and 80,000. By the time of the Buddhist restoration in the early-1980s, the number of Cambodian monks worldwide was estimated to be fewer than 3,000. The patriarchs of both Cambodian nikayas perished sometime during the period 1975–1978, though the cause of their deaths is not known. Due to their association with the Thai monarchy, monks of the Thommayut order may have been singled out for persecution. Post-Khmer Rouge era Following the defeat of the Khmer Rouge by Vietnamese forces, Buddhism initially remained officially suppressed in Cambodia. Following challenges to the legitimacy of the Vietnamese-backed People's Republic of Kampuchea, policies towards Buddhism began to ease starting in the summer of 1979. A group of monks who had been exiled and re-ordained in Vietnam during the Khmer Rouge period were sent to Cambodia, and in 1981 one of their number, Venerable Tep Vong, was elected the first sangharaja of a new unified Cambodia sangha, officially abolishing the division between the Thommayut order and the Mohanikay. The ordination of new monks was sponsored by the government as a public show of piety and lifted restrictions on ordination. Following the withdrawal of the Vietnamese military, the newly renamed Cambodian People's Party sought to align itself with the Buddhist sangha, declaring Buddhism to be Cambodia's "state religion" in a 1991 policy statement. In 1991, King Sihanouk returned from exile and appointed a new sangharaja for each of the Thommayut and Mohanikay orders, effectively marking the end of the unified system created under Vietnamese rule in 1981. The Cambodian sangha Since 1855, the Buddhist monastic community in Cambodia has been split