A member of the Roman Catholic minority, Phát joined the French-backed Vietnamese National Army which became the ARVN after the South Vietnam was established.

After having been sent to the U.S. for further training in 1958, Phát returned home to head the Civil Guard, a paramilitary force then mostly used to protect the ruling family of President Ngô Đình Diệm, rather than to counteract the communist Viet Cong (VC) insurgency.

After the January 1964 coup against Dương Văn Minh, Phát was made the commander of III Corps and also Interior Minister for a time until he was dismissed in September 1964.

In February 1965, Phát joined with fellow Catholic, Diệm protégé and Khánh opponent Phạm Ngọc Thảo – actually a communist agent intent on maximizing infighting in South Vietnam – in another coup attempt.

[citation needed] The President of South Vietnam, Ngô Đình Diệm, heavily favored Catholics, and, as a result, Phát rose quickly up the ranks.

[1] After returning to Vietnam, he served as the head of the Civil Guard,[1] a paramilitary force that was mostly used at the time to protect the ruling family of Diệm rather than to counteract the communist VC insurgency.

However, General Tôn Thất Đính, commander of the III Corps was part of the plot and deliberately refused to see Phát and told him to come back at 14:00 the following day, by which time the coup had already been scheduled to start.

In the meantime, Đính had General Trần Văn Đôn sign a counter-order transferring command of the 7th Division to his deputy and co-conspirator Nguyễn Hữu Có.

[5][6] He then phoned General Huỳnh Văn Cao, further south in the Mekong Delta's largest town, Cần Thơ, where the IV Corps was headquartered.

[8] Despite the fact that Đính saw Có as being more reliable for the purposes of staging the coup against Diệm, Minh promoted him to brigadier general immediately after the officers seized power.

[4] He was then promoted and served as the commander of III Corps, which oversaw the region of the country surrounding Saigon from 2 February until 4 April 1964, when he was replaced by Lieutenant General Tran Ngoc Tam.

[9][10] Phát was regarded as a dour military tactician who persisted with his pre-devised battleplan once hostilities had commenced, refusing to change tactics even when difficulties arose.

[11] Both were removed partly due to pressure from Buddhist activists, who accused Khánh of accommodating too many Catholic pro-Diệm elements in leadership positions.

[15] Another member of the conspiracy was Colonel Phạm Ngọc Thảo, who, while ostensibly a Catholic, was actually a communist double agent trying to maximize infighting at every possible opportunity.

[16] Four battalions of rebel troops moved before dawn towards Saigon from the Mekong Delta, with armored personnel carriers and jeeps carrying machine guns.

[9][19] In contrast to Phát's serene demeanour, his incoming troops prompted worshippers at the Roman Catholic cathedral attending mass to flee in panic.

[3] Phát and Đức failed to apprehend Khánh, who had escaped the capital and flew to the central highlands resort town of Đà Lạt.

[23] In the early hours of 14 September, before dawn, Kỳ met senior coup leaders at Tân Sơn Nhất and told them to back down, which they did.

[18] After the coup collapsed, Kỳ held a press conference claiming that the senior officers involved in the stand-off "have agreed to rejoin their units to fight the Communists", naming Phát among them.

[18] Despite the media event, Phát and Colonel Huỳnh Văn Tôn remained defiant after returning to the latter's 7th Division's headquarters in Mỹ Tho.

[25] Phát was asked about the collapse of his coup attempt and he discussed his visit to the American Embassy along with labor union leader Trần Quốc Bửu.

[33] Shortly before noon on 19 February, Thảo and Phát attacked, using some 50 tanks and a mixture of infantry battalions to seize control of the military headquarters, the post office and the radio station in Saigon.

[32][34] At the same time Phát headed towards Tân Sơn Nhất to capture the country's military headquarters with an assortment of marines, paratroopers and special forces troops.

[35] Some of the other senior officers in the Armed Forces Council were not so lucky, and they were caught by Phát's troops inside headquarters, while other buildings of the military complex remained under junta control.

[39] This turned American officials against the coup as they feared that the plotters would lead a divisive regime that would inflame sectarian tensions and play into the hands of the communists, so they decided to look for officers to defeat Thảo and Phát.

[40] Phát was supposed to seize the second largest air force base in the country, located in the satellite city of Biên Hòa outside Saigon.

[32][43][44] According to the latter version, Thảo and Phát agreed to free the members of the Armed Forces Council whom they had arrested and to withdraw in exchange for Khánh's complete removal from power.

[41] Thảo and Phát were given an appointment with the figurehead chief of state, Sửu, who was under the close control of the junta, to "order" him to sign a decree stripping Khánh of the leadership of the military.

[41] Before fleeing, Phát changed into civilian clothes and made a broadcast stating "We have capitulated", before leaving with Colonel Tôn, who had also participated in his September 1964 coup attempt.

Little is known of Phát's personal life except that he was married and, according to The New York Times, believed to have been in his late 30s when he made his coup attempts, implying he was born in the mid-to-late 1920s.