Hạnh played an important role in the Fall of Saigon when he used his authority and influence to facilitate the bloodless surrender of the South Vietnam government.

[1] Hạnh was born on 26 July 1926 at Phú Phong, Châu Thành district, Mỹ Tho province (Cochinchina), to a wealthy farming family.

He refused to take part in the pro-French village governing body and committed suicide in 1947 at the age of 72, after being unjustly humiliated by a Moroccan French soldier.

He became Minh's staff chief in early 1955 and took over the area of Rừng Sác, Chợ Lớn province, Gia Định, Tây Ninh and Saigon city.

Hạnh assisted Nguyễn Hữu Có in capturing the headquarters of the 2nd Division and prevented IV Corps from rescuing Diệm.

[4] Hạnh's military career suffered under the presidency of Nguyễn Văn Thiệu, who considered Minh and his associates as rivals.

He was forced to retire in May 1974 at the age of 48 under a rule restricting military service to 20 years, a move used by Thiệu to purge his political opponents.

On the other hand, Hạnh became dissatisfied with United States intervention in South Vietnamese politics, which he considered as a gross violation of Vietnam's sovereignty.

[2][5] Hạnh finally agreed to work as an intelligence agent for the VC under the pseudonym "Morning Star" and codename S7.

[5][3] In early 1975 he confirmed that the ARVN was unable to recover its losses to the People's Army of Vietnam (PAVN) at the Battle of Phước Long.

During the offensives of 1975, Hạnh encouraged the PAVN to make rapid advances and leave the liberated areas to the local defense forces without the risk of being attacked at the rear.

[3] After the collapse of ARVN defenses at Xuân Lộc and Phan Rang, the PAVN approached Saigon and prepare for its final offensive in late April 1975.

On 30 April at 9:30 AM, Minh and Nguyễn Hữu Hạnh broadcast their announcements to cease all resistance and ordered all ARVN soldiers and officers to follow suit.

Hạnh also contacted general Nguyễn Khoa Nam, commander of IV Corps in the Mekong Delta, to obey the orders of Minh.

He was recognized as a patriotic figure, was elected as the Secretary of People's Association for School Guardian and became a Committee Member of the Vietnamese Fatherland Front.