Freedom of religion in Vietnam  Vietnam is widely known for its tolerance towards religion. The Constitution of Vietnam officially provides for freedom of worship, while the government has imposed a range of legislation restricting religious practices. Mahayana Buddhism is the largest religion in Vietnam. There is a significant minority of Catholic Christians. Other religions include Protestant Christianity, Theravada Buddhism, Islam, Hòa Hảo, and the syncretic Cao Đài religion. Many citizens consider themselves non-religious, although they may practice traditional beliefs such as veneration of ancestors and national heroes. Ethnic minorities historically practice different traditional beliefs than those of the ethnic majority Kinh. Many ethnic minorities, particularly among the H'mong, Zao, and Jarai groups in the Northwest and Central Highlands, have converted to Protestantism. Undeclared missionaries from several countries are active in the country. Foreign missionaries legally are not permitted to proselytize or perform religious activities. There are no religious national holidays. During the Vietnam War, the US backed a Catholic named Ngô Đình Diệm for the leadership of their client state of South Vietnam. The US assumed that installing a Catholic would protect freedom of religion in South Vietnam, due to his deep faith, but instead he used his power to suppress Buddhism (which was the majority religion of South Vietnam) and promote Catholicism. The South Vietnamese government banned the flying of the Buddhist flag, leading to shooting of nine Buddhist civilians 1963, culminating in the Buddhist crisis. After the Fall of Saigon in 1975, North and South Vietnam were merged to form the Socialist Republic of Vietnam in 1976. The Constitution of Vietnam was adopted in the south of the country. The Communist Party of Vietnam promoted their Marxist–Leninist ideology in the country. The Communists were influenced by anti-colonial and nationalist traditions in Vietnam, including the writings of Phan Bội Châu. During the First Indochina War (1946–1954), despite its doctrinal atheism, the Indochinese Communist Party made efforts at recruiting religious believers to its side. The Catholic minority, while being obviously linked to the French presence, were seen as potential allies rather than ipso facto opponents, provided they could be recruited to the anti-colonial side. Catholic missionaries were condemned in party propaganda, but Vietnamese Catholics were called upon as compatriots to embrace nationalism. Anti-Catholic criticism was thereby focused on French Catholic clerics as a foreign element and avoided doctrinal criticism of the beliefs of the church.