Major General Tôn Thất Xứng was an officer of the Army of the Republic of Vietnam

Army of the Republic of Vietnam

The Army of the Republic of Viet Nam , sometimes parsimoniously referred to as the South Vietnamese Army , was the land-based military forces of the Republic of Vietnam , which existed from October 26, 1955 until the fall of Saigon on April 30, 1975...

.

He served as the commander of I Corps

I Corps (South Vietnam)

The I Corps Tactical Zone was a corps of the Army of the Republic of Vietnam , the army of the nation state of South Vietnam that existed from 1955 to 1975. It was one of four corps which the ARVN oversaw. This was the northernmost region of South Vietnam, bordering North Vietnam...

, which oversaw the northernmost part of the country, from 30 January 1964 until 14 November of the same year, when he was replaced by Lieutenant General Nguyen Chanh Thi

Nguyen Chanh Thi

Lieutenant General Nguyễn Chánh Thi was an officer in the Army of the Republic of Vietnam . He is best known for frequently being involved in coups in the 1960s and wielding substantial influence as a key member of various juntas that ruled South Vietnam from 1964 until 1966, when he was...

. Xung was installed on the day of the successful coup

1964 South Vietnamese coup

Before dawn on January 30, 1964, General Nguyen Khanh ousted the military junta led by General Duong Van Minh from the leadership of South Vietnam without firing a shot. It came less than three months after Minh's junta had themselves come to power in a bloody coup against then President Ngo Dinh...

 by General Nguyen Khanh

Nguyen Khanh

Nguyễn Khánh is a former general in the Army of the Republic of Vietnam who variously served as Head of State and Prime minister of South Vietnam while at the head of a military junta from January 1964 until February 1965. He was involved in or against many coup attempts, failed and successful,...

 that toppled the military junta of General Duong Van Minh

Duong Van Minh

Minh was born on 16 February 1916 in Mỹ Tho Province in the Mekong Delta, the son of a wealthy landowner who served in a prominent position in the Finance Ministry of the French colonial administration...

.Tucker, pp. 526–533.