After several years in exile in Japan, the United States, and Europe, Diệm returned home in July 1954 and was appointed prime minister by Bảo Đại, against the French suggestion of Nguyen Ngoc Bich (a French-educated engineer, Francophile anticolonialist, a resistance hero in the First Indochina War, and medical doctor) as an alternative.

Historian Edward Miller stated that Diệm "displayed Christian piety in everything from his devotional practices to his habit of inserting references to the Bible into his speeches"; he also enjoyed showing off his knowledge of classical Chinese texts.

[18] After graduating at the top of his class in 1921, Diệm followed in the footsteps of his eldest brother,[tone] Ngô Đình Khôi, joining the civil service in Thừa Thiên as a junior official.

[17] Diệm's rise was also facilitated through his brother Ngô Đình Khôi's marriage to the daughter of Nguyễn Hữu Bài, who was the Catholic head of the Council of Ministers at the Huế court.

In 1945, after the coup against French colonial rule, the Japanese offered Diệm the post of prime minister in the Empire of Vietnam under Bảo Đại, which they organized on leaving the country.

[29] Diệm also secretly maintained contact with high-ranking leaders of the Democratic Republic of Vietnam, attempting to convince them to leave Hồ Chí Minh's government and join him.

The first of these were Catholic nationalism, which Diệm inherited from his family's tradition, especially from his brother Bishop Ngô Đình Thục and Nguyễn Hữu Bài, who advised him to "return the seal" in 1933 to oppose French policies.

Lastly, instructed by Ngô Đình Nhu, Diệm began to examine Personalism, which originated from French Catholicism's philosophy and then applied this doctrine as the main ideology of his regime.

The Diệm regime also provided them with food and shelter, farm tools, and housing materials as well as digging irrigation canals, building dykes, and dredging swamp-lands to help stabilise their lives.

[53] In early 1955, although American advisors encouraged Diệm to negotiate with the leaders of the political-religious forces who threatened to overthrow his position and to forge an anti-communist bloc, he was determined to attack his enemies to consolidate his power.

Although neither Cẩn nor Nhu held any official role in the government, they ruled their regions of South Vietnam absolutely, commanding private armies and secret police forces.

[78] South Vietnam was divided into colonial-era provinces, of which governors enjoyed sweeping powers and firmly controlled local administrations, creating a problem of corruption and cronyism.

While the monarch was highly unpopular given his collaboration with the French colonial regime, the new government committed to further diminishing Đại's reputation with aggressive smear campaign and large pro-rallies.

Additionally, the referendum itself was considered non-secret, given that the voters were given ballots with the photos of Diệm and Bảo Đại on it and were supposed to tear it in half and deposit the slice with their preferred candidate into the box – this made one's choice visible to everyone.

The government hailed the process as democratic and transparent, given how the Assembly meetings were open and media presence was allowed; the National Revolutionary Movement dominated the council, but a handful of opposition figures had won seats as well.

[93] Resettlement According to Miller, Diệm, who described tenant farmers as a "real proletariat" and pursued the goal of "middle peasantization", was not a beholden to large landowners, instead of vigorously implementing Land Reform, Diệm had his own vision in Vietnamese rural development based on resettlement, which focused on redistribution of people (rather than land), could reduce overpopulation and lead to many benefits in socio-economic transformation as well as military affairs and security, especially anti-communist infiltration.

[97] Miller argues that Diệm expressed "genuine desire to end the exploitation and misery that afflicted millions of South Vietnamese rural residents", and wished to support poor peasantry by gradual modernisation and moderate redistribution of land.

Diệm considered resettlement an important part of his economic nationalism, arguing that utilising Vietnamese land would increase the production of grains and rubber and allow South Vietnam to enter international trade.

This project created an intense social conflict between the settlers and Cai San natives, and Diệm offered a concession to the local landowners by decreeing that refugees must sign rental contracts with them.

[100] While initially considered a failure, especially due to the fact that the resettlement sparked anti-government sentiment and created social conflicts, Miller notes that Cai San became fairly prosperous by 1960, and the settlement did gradually evolve into a pro-government stronghold, thus succeeding in its aim at counter-insurgency.

[101] During his presidency, Diệm strongly focused on his central concern: internal security to protect his regime as well as maintain order and social change: staunch anti-subversion and anti-rebellion policies.

[119] 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.

[145] Nhu's purpose in leaking the meeting was to blackmail the United States with the message that if Kennedy continued to criticize Diệm's handling of the Buddhist crisis, Diem would reach an understanding with the Communists.

[148] Jerema Słowiak of Jagiellonian University notes that the American media coverage skewed the true background of the conflict, spreading the "narrative of evil dictator Diệm oppressing good, peaceful Buddhists".

[119] Thích Trí Quang, the leader of the Buddhist movement, insisted that the agitation must not stop until the South Vietnamese government is overthrown, and stated his intention to "call for suicide volunteers" if necessary.

Lieutenant Colonel Lucien Conein, a CIA officer, had become a liaison between the US Embassy and the generals, who were led by Trần Văn Đôn, and they met each other for the first time on 2 October 1963, at Tân Sơn Nhất airport.

[161] Conein then delivered the White House's message of American non-intervention, which was reiterated by Henry Cabot Lodge Jr., the U.S. ambassador, who gave secret assurances to the generals that the United States would not interfere.

On 2 November 1963, the brothers were assassinated together in the back of an M113 armored personnel carrier with a bayonet and revolver by Captain Nguyễn Văn Nhung, under orders from Minh[165] given while en route to the Vietnamese Joint General Staff headquarters[citation needed].

[169] The North Vietnamese Politburo was more explicit:The consequences of the 1 November coup d'état will be contrary to the calculations of the US imperialists ... Diệm was one of the strongest individuals resisting the people and Communism.

[178] The South Vietnamese army would gradually gain experience and skill in both warfare and intelligence under Diệm's command, and his assassination turned the tide in favor of the north, with the subsequent governments proving inefficient and incapable of organising successful resistance to Viet Cong advances.