Throughout 1964 and 1965, as South Vietnam was struggling to establish a stable state after the ouster of Diệm, Thảo was involved in several intrigues and coup plots which diverted the government from implementing its programs.

[3][4] In his high school years at the Lycée Chasseloup-Laubat,[5] Thảo met Trương Như Tảng, who later became a high-ranking member of the Viet Cong (VC), a communist guerrilla organisation in South Vietnam.

[3][6] Despite being educated at an upper-class school that served children of French colonial administrators and privileged Vietnamese—French was the medium of instruction and Gallic culture and history a major part of the curriculum[7]—Thảo was attracted to nationalist politics.

[3][4] In September 1945, Hồ declared independence under the Democratic Republic of Vietnam (DRV) following the withdrawal of Imperial Japan, which had seized control of the country from France during the Second World War.

[15] Following the French defeat in 1954 at Điện Biên Phủ, Thảo helped evacuate communist fighters from South Vietnam and Cambodia in accordance with the terms of the Geneva Conference.

[3][4] Under these Accords, Vietnam was to be temporarily divided at the 17th parallel pending national elections to reunify the country in 1956, and military personnel were to be evacuated to their respective sides of the border.

[3][4] At the same time, one of Thảo's brothers had been appointed as North Vietnam's ambassador to East Germany, having served as vice chairman of the Việt Minh's Resistance Committee for the South during the war against the French.

The VC were dominated by communists, but portrayed itself as a nationalist militant organisation, stating its aim to be the "reunification of the fatherland" with the overthrow of the "disguised colonial regime of the U.S. imperialists and the dictatorial Ngo Dinh Diem administration".

Thục put Thảo in touch with Trần Kim Tuyến, who was in charge of intelligence operations under Diệm's younger brother Nhu, who was the head of the secret police and controlled the ARVN Special Forces.

[26] As a result of his family's Catholic connections, Thảo rose steadily in the ARVN, since Diệm's regime had always promoted officers primarily on religious preference and loyalty.

[3][4] As Thảo kept a close watch on those who commanded troops, lest they use their personnel in a coup, the leading officers were keen to maintain a good relationship with him, which increased his effectiveness as a spy.

[32] In one operation by Thảo's ARVN forces, American field journalists covering the battle saw their hours-long attempt to box in a VC battalion yield only one farmer who lived in a hut with antigovernment slogans.

[3][4][33] In fact, the Pulitzer Prize-winning journalist David Halberstam misinterpreted the lack of attacks in Bến Tre, while other provinces were being ravaged, as proof that Thảo was one of the few capable government officials in the Mekong Delta.

[34] Journalist Robert Shaplen wrote: "In all respects, Thao is one of the most remarkable Vietnamese around, being a conspiratorial revolutionary figure straight out of a Malraux novel and, at the same time, a highly sophisticated and astute man, whose talents, if only they were properly channeled, could profitably be used right now."

[49] Thảo commanded around two dozen tanks, which formed a column in the streets surrounding the Gia Long Palace at midnight, and helped launch the full-scale attack at 03:30 on 2 November.

[51] The brothers subsequently surrendered to an ARVN convoy led by General Mai Hữu Xuân at a nearby Catholic church and were executed en route to military headquarters despite being promised safe exile.

The journalists' reporting of Diệm's authoritarian rule, military failures,[53] and attacks on Buddhists shifted American public opinion and put pressure on Washington to withdraw support for the Ngô family and seek a change of leadership.

[62] After the fall of the Diệm regime, Thảo was designated by the head of state Minh and the civilian Prime Minister Nguyễn Ngọc Thơ to create the nucleus of a group called the Council of Notables, and promote it to the public.

[14] With Khánh's grip on power shaky, an anonymous source said that Thảo was worried about how he would be treated if someone else took over: "Thao acted first, out of fear that if he did not, the other generals would overthrow Khanh and get rid of him as well.

[88] Shortly before noon on 19 February, he used around 50 tanks, their crew and a mixture of infantry battalions to seize control of the military headquarters, the post office and the radio station of Saigon.

His plane lifted off from Tan Son Nhut Air Base, the country's military headquarters, just as rebel tanks were rolling in, attempting to block the runway.

[91] U.S. government analysts concluded that the rebellion was "primarily a move by die-hard neo-Diemists and Catholic military militants, disturbed at the rise of Buddhist influence, opposed to Gen. Khánh and—in a vague, ill-thought-out way—desirous of turning back the clock and undoing some of the results of the November 1963 ouster of Diem.

[81] Although Taylor and US military commander General William Westmoreland wanted Khánh out, the pro-Diệm political ideology expressed by Thảo's supporters alienated them, as they feared that the coup plotters would destabilize and polarize the country if they took power.

[95] However, as night came, senior military opinion began to turn against Thảo and Phát, although it was not clear at this stage whether the anti-Thảo forces being organised and led by Thi were hostile to Khánh as well.

The coup collapsed when, between midnight and dawn, anti-Thảo forces swept into the city from the south along with some components of the 7th Airborne Brigade loyal to Kỳ from Biên Hòa in the north.

Whether the rebels were genuinely defeated by the overwhelming show of strength or whether a deal was struck with Kỳ to end the revolt in exchange for Khánh's removal is disputed, although a large majority support the latter.

[79][86][97][98][99] According to the latter version, Phát and Thảo agreed to free the members of the Armed Forces Council that they had arrested and withdraw in exchange for Khánh's complete removal from power.

[97] During the early morning, while the radio station was still in the hands of Thảo's men, a message attributed to Sửu was read out; it claimed that the chief of state had sacked Khánh.

[101] While in hiding in Catholic villages, Thảo expressed his willingness to surrender and cooperate with Quát's government, if he and approximately 50 officers involved in the coup were granted amnesty.

[106] Tảng, who later abandoned communism, said that Thảo "was a nationalist, not an ideologue",[111] and credited him with turning the military tide towards the communists by helping to bring down Diệm and fomenting chronic instability and infighting for 18 months.