He converted to Roman Catholicism to curry favor with Diệm and headed the military wing of the Cần Lao party, a secret Catholic organization that maintained the Ngôs' grip on power.

At the age of 32, Đính became the youngest ever ARVN general and the commander of the II Corps, but he was regarded as a dangerous, egotistical, and impetuous figure with a weakness for alcohol and partying.

In 1962, Đính, whom Diệm regarded as one of his most loyal officers, was appointed commander of the III Corps that oversaw the region surrounding the capital Saigon, making him important to the prospects of any coup.

Following Khánh's exile by another group of generals, Đính was appointed to command the I Corps in 1966 and ordered to put down the Buddhist Uprising, but Prime Minister Nguyễn Cao Kỳ disapproved of his conciliatory policies.

Đính was born in the central highlands resort town of Da Lat on November 20, 1926,[1] into the Tôn Thất family of Huế that were relatives of the Nguyễn dynasty.

[6] Within six years of enlisting in the military, Đính had risen to the rank of colonel and was made the inaugural commander of the newly formed 32nd Division based in Da Nang in the centre of the country on January 1, 1955.

[7] In August 1963, Nhu, who controlled the special forces and secret police, allowed Đính to have a hand in planning raids against Buddhist dissidents who had been organising at the Xá Lợi pagoda,[8] Saigon's largest.

"[24] In the aftermath of the raids, Foreign Minister Vũ Văn Mẫu resigned in protest, shaved his head like a monk and sought to leave on a pilgrimage to India; Nhu ordered Đính to jail him.

[8][26] In the heady times after the attacks, Đính had a "somewhat incoherent" debate with his American advisor, claiming "he [Đình] was without doubt the greatest general officer in the ARVN, the saviour of Saigon ... and soon he would be the top military man in the country.

[29] His colleagues, led by General Trần Văn Đôn, were plotting a coup against Diệm because of the Buddhist crisis, and attempted to play on Đính's ego to convince him to join them.

[8] In a series of meetings, the other generals assured Đính that he was a national hero worthy of political authority, and claimed that Nhu had not realised how important he was in the future of the country.

[6][30] The other generals told him that the people were dissatisfied with Diệm's cabinet, that Vietnam needed dynamic young officers in politics, and that their presence would reverse the declining morale in the ARVN.

[31] With Đính and the Ngô family's increasing focus on the political usage of the army, the military situation in III Corps deteriorated badly in the second half of 1963, as personnel were redeployed into the cities.

In August, he moved a unit away from Bến Tượng, which had been portrayed as a model settlement in the Strategic Hamlet Program that was supposed to isolate peasants into fortified villages to keep the Viet Cong out.

[31] Codenamed Operation Bravo, the first stage of the scheme would involve some of Đính and Tung's loyalist soldiers, disguised as insurgents led by apparently renegade junior officers, faking a coup and vandalizing the capital.

The loyalists and some of Nhu's underworld connections would also kill some figures who were assisting the conspirators, such as the titular but relatively powerless Vice President Nguyễn Ngọc Thơ, CIA agent Lucien Conein (who was on assignment in Vietnam as a military adviser) and Ambassador Lodge.

[12][38][39] Đính was put in charge of the fake coup and was allowed the additional control of the 7th Division based in Mỹ Tho, which was previously assigned to Diệm loyalist Cao, who commanded the IV Corps in the Mekong Delta.

The reassignment of the 7th Division gave Đính and his III Corps complete encirclement of Saigon, and would prevent Cao from storming the capital to save Diệm as he had done during the coup attempt in 1960.

[43] He boasted to the media that he and his troops were responsible for seizing broadcasting studios, the police headquarters, Tân Sơn Nhứt Air Base, and the release of hundreds of political prisoners such as monks and students.

[51] Eventually Minh, the head of the military junta, struck a compromise whereby Đính was made Security Minister and Administrative Affairs, which partially covered the interior ministry.

[53] Đính and the new national police chief, General Xuân, were accused of arresting people en masse, before releasing them in return for bribes and pledges of loyalty.

In interviews with The Washington Post and The New York Times, he claimed that he took a leading role in the coup because "we would have lost the war under Diệm" and saying that he participated "not for personal ambition, but for the population, the people and to get rid of Nhu".

[61] US Secretary of Defense Robert McNamara criticised the arrangement,[62] and in early January 1964, Đính was relieved by General Khiệm, who had been the head of the armed forces until being demoted after the coup against Diệm, and he set about overthrowing the MRC.

[63] Đính's political stay was brief, as General Nguyễn Khánh, who was disgruntled at not receiving a high position after Diệm's removal, deposed the MRC with the support of Khiệm on January 30, 1964, without firing a shot.

Khánh had them arrested, claiming that they were part of a neutralist plot with the French government of President Charles de Gaulle to make a peace deal with North Vietnam that would not end communism.

"[67] During the period of house arrest, Khánh briefly released Đính and Kim when the United Front for the Liberation of Oppressed Races, known by its French acronym of FULRO, launched an uprising in the central highlands calling for autonomy for indigenous people.

Đính and Kim were sent to Ban Mê Thuột in an attempt to end the standoff in September 1964, but after negotiations stalled, they conferred with Khánh and decided to order ARVN troops to crush the rebellion, which was carried out successfully.

[71] With the rise to power of Nguyễn Cao Kỳ – head of the Republic of Vietnam Air Force – following Khánh's departure, returned to a command role in the army.

[74] On April 19, clashes erupted in Quảng Ngãi between the Buddhists and the VNQDĐ (Vietnamese Nationalist Party), which supported the continuation of the anti-communist war, prompting Đính to forcibly restrain the two groups.

[80] Đính left the army and upon the nominal restoration of civilian rule, won election to the newly created Senate in 1967, as part of the Hoa Sen (Lotus) ticket.