In a country where surveys of the religious composition estimated the Buddhist majority to be between 70% and 90%, Diệm's policies generated claims of religious bias.
Diem was widely regarded by historians as having pursued pro-Catholic policies that antagonized many Buddhists.
Specifically, the government was regarded as being biased towards Catholics in public service and military promotions, as well as the allocation of land, business favors and tax concessions.
Diệm also once told a high-ranking officer, forgetting that he was a Buddhist, "Put your Catholic officers in sensitive places.
They can be trusted."
Many officers in the Army of the Republic of Vietnam converted to Catholicism in the belief that their military prospects depended on it.
The distribution of weapons to village self-defense militias intended to repel Việt Cộng guerrillas saw weapons only given to Catholics.
Some Buddhist villages converted en masse to Catholicism in order to receive aid or to avoid being forcibly resettled by Diệm's regime, with Buddhists in the army being denied promotion if they refused to convert to Catholicism.
Some Catholic priests ran their own private armies, and in some areas forced conversions, looting, shelling and demolition of pagodas occurred.

The Catholic Church was the largest landowner in the country, and the "private" status imposed on Buddhism by the French required official permission to conduct public Buddhist activities and was never repealed by Diệm.
Catholics were also de facto exempt from the corvée labor that the government obliged all citizens to perform; US aid was disproportionately distributed to Catholic-majority villages.
The land owned by the Catholic Church was exempt from land reform.
Under Diệm, the Catholic Church enjoyed special exemptions in property acquisition, and in 1959, Diệm dedicated his country to the Virgin Mary.
The white and gold Vatican flag was regularly flown at all major public events in South Vietnam.
The newly constructed Hue and Dalat universities were placed under Catholic authority to foster a Catholic-skewed academic environment.
Nonetheless, Diệm had contributed to Buddhist communities in South Vietnam by giving them permission to carry out activities that were banned by French and supported money for Buddhist schools, ceremonies, and building more pagodas.
Among the eighteen members of Diệm's cabinet, there were five Catholics, five Confucians, and eight Buddhists, including a vice-president and a foreign minister.
Only three of the top nineteen military officials were Catholics.

The regime's relations with the United States worsened during 1963, as discontent among South Vietnam's Buddhist majority was simultaneously heightened.
In May, in the heavily Buddhist central city of Huế, where Diệm's elder brother was the Catholic Archbishop, the Buddhist majority was prohibited from displaying Buddhist flags during Vesak celebrations commemorating the birth of Gautama Buddha when the government cited a regulation prohibiting the display of non-government flags.
A few days earlier, however, white and yellow Catholic papal flags flew at the 25th anniversary commemoration of Ngô Đình Thục's elevation to the rank of bishop.
According to Miller, Diệm then proclaimed the flag embargo because he was annoyed with the commemoration for Thục.
However, the ban on religious flag led to a protest led by Thích Trí Quang against the government, which was suppressed by Diệm's forces, and unarmed civilians were killed in the clash.
Diệm and his supporters blamed the Việt Cộng for the deaths and claimed the protesters were responsible for the violence.
Although the provincial chief expressed sorrow for the killings and offered to compensate the victims' families, they resolutely denied that government forces were responsible for the killings and blamed the Viet Cong.
According to Diệm, it was the communists who threw a grenade into the crowd.

The Buddhists pushed for a five-point agreement: freedom to fly religious flags, an end to arbitrary arrests, compensation for the Huế victims, punishme
In a country where surveys of the religious composition estimated the Buddhist majority to be between 70% and 90%, Diệm's policies generated claims of religious bias. Diem was widely regarded by historians as having pursued pro-Catholic policies that antagonized many Buddhists. Specifically, the government was regarded as being biased towards Catholics in public service and military promotions, as well as the allocation of land, business favors and tax concessions. Diệm also once told a high-ranking officer, forgetting that he was a Buddhist, "Put your Catholic officers in sensitive places. They can be trusted." Many officers in the Army of the Republic of Vietnam converted to Catholicism in the belief that their military prospects depended on it. The distribution of weapons to village self-defense militias intended to repel Việt Cộng guerrillas saw weapons only given to Catholics. Some Buddhist villages converted en masse to Catholicism in order to receive aid or to avoid being forcibly resettled by Diệm's regime, with Buddhists in the army being denied promotion if they refused to convert to Catholicism. Some Catholic priests ran their own private armies, and in some areas forced conversions, looting, shelling and demolition of pagodas occurred.
The Catholic Church was the largest landowner in the country, and the "private" status imposed on Buddhism by the French required official permission to conduct public Buddhist activities and was never repealed by Diệm. Catholics were also de facto exempt from the corvée labor that the government obliged all citizens to perform; US aid was disproportionately distributed to Catholic-majority villages. The land owned by the Catholic Church was exempt from land reform. Under Diệm, the Catholic Church enjoyed special exemptions in property acquisition, and in 1959, Diệm dedicated his country to the Virgin Mary. The white and gold Vatican flag was regularly flown at all major public events in South Vietnam. The newly constructed Hue and Dalat universities were placed under Catholic authority to foster a Catholic-skewed academic environment. Nonetheless, Diệm had contributed to Buddhist communities in South Vietnam by giving them permission to carry out activities that were banned by French and supported money for Buddhist schools, ceremonies, and building more pagodas. Among the eighteen members of Diệm's cabinet, there were five Catholics, five Confucians, and eight Buddhists, including a vice-president and a foreign minister. Only three of the top nineteen military officials were Catholics.
The regime's relations with the United States worsened during 1963, as discontent among South Vietnam's Buddhist majority was simultaneously heightened. In May, in the heavily Buddhist central city of Huế, where Diệm's elder brother was the Catholic Archbishop, the Buddhist majority was prohibited from displaying Buddhist flags during Vesak celebrations commemorating the birth of Gautama Buddha when the government cited a regulation prohibiting the display of non-government flags. A few days earlier, however, white and yellow Catholic papal flags flew at the 25th anniversary commemoration of Ngô Đình Thục's elevation to the rank of bishop. According to Miller, Diệm then proclaimed the flag embargo because he was annoyed with the commemoration for Thục. However, the ban on religious flag led to a protest led by Thích Trí Quang against the government, which was suppressed by Diệm's forces, and unarmed civilians were killed in the clash. Diệm and his supporters blamed the Việt Cộng for the deaths and claimed the protesters were responsible for the violence. Although the provincial chief expressed sorrow for the killings and offered to compensate the victims' families, they resolutely denied that government forces were responsible for the killings and blamed the Viet Cong. According to Diệm, it was the communists who threw a grenade into the crowd.
The Buddhists pushed for a five-point agreement: freedom to fly religious flags, an end to arbitrary arrests, compensation for the Huế victims, punishme
Ngo Dinh Diem