Vân's vocal opposition to the policies of President Nguyễn Văn Thiệu led to surveillance by the national police and numerous arrests.

[8][9] Although he qualified for a teaching post at the University of Indochina in Hanoi, as her father was an indigenous Vietnamese, he instead was sent to a rural area to practice veterinary medicine.

[6] Vân attended a private Catholic school in Da Lat, where she was one of the only two Vietnamese students – the other pupils were all children of French officials or the monarch Bảo Đại.

Because many students needed to work and could not attend classes, Vân used her shorthand to make note of the lectures of her professors and then typed them out and sold them to her classmates.

[2] After completing her LL.M at Columbia in 1959,[12][13][Note 3] Vân returned to Europe and taught briefly at the International University of Comparative Law, headquartered in Luxembourg and Strasbourg,[10] while researching legal systems in Latin America.

At one meeting hosted by the British Embassy to discuss Operation Rolling Thunder, she was asked by experts including the ambassadors Gordon Etherington-Smith (UK) and Henry Cabot Lodge Jr. (USA), and the military experts Sir Robert Grainger Ker Thompson (UK) and General William Westmoreland (USA), if the bombing strategy would be effective.

[16][17] Ignoring her advice and proceeding with the bombing raids led Vân to become a relentless protester against the policies of the government of South Vietnam and "American imperialists".

[18][19] She was arrested in early 1965 along with her father, who led the Committee for Peace, and Trương Như Tảng, leader of the National Self-Determination Group.

The Third Force coalition, which was both anti-war and anti-communist, worked towards a democratic post-war solution with improved socio-political rights and protections.

She argued for an immediate withdrawal of American troops and a pledge from the United States to provide post-war economic support to rebuild the country.

President Thiệu, interpreting their actions as dangerous to his regime, ordered troops to turn the women away and threaten to destroy their facilities.

[25] She was arrested in July 1971 for lodging a complaint at the Supreme Court when it was announced that no opposition to Thiệu would be allowed to run in the upcoming election.

Although she was released,[29] she was arrested again in September for a protest outside the National Assembly of the Republic of Vietnam and charged with disturbing the peace and illegal association.

[34][35] Struggles with asthma and lumbago, which led to partial paralysis of her right leg, resulted in Vân's move to a prison hospital in April 1973.

[13][36] Radical feminist and US congresswoman Bella Abzug flew to Vietnam and brought her case to the attention of the US legislature and President Richard Nixon, who made an appeal for her release.

[31][37][38] Although WILPF members had secured offers for a guest professorship at Columbia University and Bryn Mawr College following her release,[42] Vân was doubtful that she would be permitted to leave the country.

[45] She continued to press for a political solution to end the war because, despite the US troop withdrawal, neither of the combatants was willing to lose strength and initiate demobilization.

The organization was sponsored by the government and focused on developing projects to expand the social and scientific roles of women and work with legislators to draft policies to facilitate growth.

[55] Some of the Vietnamese diaspora believed she was on a quest for fame, whereas others felt that by working in the socialist government, Vân had turned her back on the ideals of the Third Force Movement's fight against war and communism.

[9] Lưu Văn Đạt, the General Secretary and Vice President of the Vietnam Lawyers Association acknowledged that Vân's work on the law committee of the Vietnamese National Assembly was critically important.

[9] She was elected four times and her terms were marked by criticism of the government's lack of socio-economic freedoms and failure to provide adequate justice structures.

[23][Note 5] Unlike other feminist groups of the time or in Vietnam's past, the organization maintained its autonomy from political alliances and cultivated diversity of members across a wide spectrum of society, giving women a means of pressing for representation, self-determination, and peace.