On 22 February, in Tây Ninh, representatives from the Bình Xuyên criminal gang along with the religious sects Cao Đài, Hòa Hảo, Dân Xã Đảng and Liên Minh formed the United Front against Prime Minister Ngô Đình Diệm, posing a severe challenge to Diệm’s increasingly dictatorial rule. Bình Xuyên, covertly aided by French advisors still in South Vietnam, controlled the National Police led by Lê Văn Viễn, whose power was focused in Saigon. The Cao Đài and Hòa Hảo sectarian armies wanted positions in Diệm’s cabinet and complete administrative control over the areas in which they had large numbers of followers.
On 28 April, against advice from the US – who increasingly believed that Diệm be replaced – against advice from the French and advice from his cabinet, Diệm moved against the United Front. In what is referred to as the Battle of Saigon, within a few months Diệm’s Army of the Republic of Vietnam (ARVN) eliminated most of Bình Xuyên’s 40,000 armed soldiers throughout the city, leaving only a few small bands who fled Saigon and joined communist forces in the countryside. The leader of Bình Xuyên, Bảy Viễn, escaped to Paris with French assistance. Casualties on both sides plus civilians amounted to approximately 500 dead, 1000 wounded and 20,000 made homeless due to widespread destruction over a square mile of Saigon.
Neither the Cao Đài nor the Hòa Hảo armies joined the Bình Xuyên in the Battle of Saigon, swayed by bribes paid by Diệm and Colonel Edward Lansdale that forced them to remain neutral or to unite their armed forces with the fledgeling ARVN.
After the defeat of Bình Xuyên, the authority and prestige of Diệm’s government increased as well as US support for him as leader of the Republic of Vietnam (RVN). He was even applauded in the US, publisher Henry Luce declaring:
Henry Luce writing for Life as documented in Seth Jacobs, Cold War Mandarin, 2006, Rowman & Littlefield Publishers New York
With the Bình Xuyên vanquished, Diệm turned his attention to conquering the Cao Đài and Hòa Hảo. On 5 June, ARVN troops began battling Hòa Hảo forces in Cần Thơ. Five Hòa Hảo battalions surrendered immediately; their Commander Ba Cụt and three remaining leaders fled over the Cambodian border along with 3,000 armed men. The other leaders soon surrendered but Ba Cụt and his 3,000 armed men continued to resist the army until 1956.
In October, Ngô Đình Diệm ordered the army to march on the Cao Đài political centre in Tây Ninh. The Cao Đài pope, Phạm Công Tắc, was forced to flee to Cambodia, where he died in 1959. Most other Cao Đài leaders chose to rally to Diệm’s government, which then allowed Diệm to dismantle the Cao Đài private army and absorb it into the ARVN. By the end of 1955, Diệm had almost taken control of South Vietnam, and his government was stronger than ever before.
Bolstered by his new-found power and US support, Diệm refused to enter into talks with North Vietnam concerning the 1956 election to unify the country as stipulated by the Geneva Accords. Diệm called a national election in October and easily defeated Head of State Bảo Đại, thus becoming President of the new Republic of Vietnam.