An Army of the Republic of Vietnam general, Nguyen Khanh led a bloodless military coup that overthrew the Military Revolutionary Council that overthrew and killed Ngo Dinh Diem. Khanh's coup in January 1964 followed the November 1963 overthrow of Diem, of which he was not a member.
Khanh had been Diem's army chief of staff at the time of the 1960 coup by the ARVN Airborne Brigade, which was disturbed over both Diem's favoritism for loyalists but failure to stop the VC. He took command of the defense, obtaining key assistance from Tran Thien Khiem. 
In August 1963, the Central Intelligence Agency considered him a competent commander. It was suggested that Diem had rewarded him, making him JGS Chief of Staff, for helping stop a 1960 coup. He moved on to command II Corps tactical zone.
After the November coup, Khanh told Lucien Conein of his dissatisfaction, but neither he nor Henry Cabot Lodge Jr. took it seriously. Khanh sought U.S. support for his coup by claiming Duong Van Minh and Tran Van Don were really supporters of Charles de Gaulle and wanted a more neutralist solution than was consistent with U.S. policy. 
Khanh, in later governments, allowed various amounts of token civil control. In August 1964, after a controversial call to "go north", Khanh removed Minh and assumed the presidency, resigning it two weeks later. In September, he formed the High Legislative Council to form a new government. The HLC named Pham Khac Suu as head of state and Tran Van Huong as Premier and head of government.
The HLC then came under the control of Khanh, Duong Van Minh and Tran Thien Khiem formed a triumvirate, althugh Khanh was reported "ill" a week later. Nguyen Xuan Oanh, an economist, was then named to run a subordinate civilian government, over Buddhist calls for all-civilian government.
In February 1965, General Nguyen Van Thieu, with Ky, overthrew Khanh. Khanh was replaced by Ky, who became premier in June. Khanh took a symbolic "ambassador-at-large" job and left Vietnam, never to return. 
- Moyar, Mark (2006), Triumph Forsaken, Cambridge University Press, pp. 109-112
- Office of Current Intelligence, Central Intelligence Agency; annotations by McGeorge Bundy (August 28, 1963), "Cast of Characters in South Vietnam,", in John Prados, JFK and the Diem Coup, vol. George Washington University National Security Archive Electronic Briefing Book No. 101, OCI 2703/63
- Karnow, Stanley (1983), Vietnam, a History, Viking Press, pp. 337-338
- Karnow, p. 385