1965 South Vietnamese coup

On February 19, 1965, some units of the Army of the Republic of Vietnam commanded by General Lâm Văn Phát and Colonel Phạm Ngọc Thảo launched a coup against General Nguyễn Khánh, the head of South Vietnam's ruling military junta. Their aim was to install General Trần Thiện Khiêm, a Khánh rival who had been sent to Washington D.C. as Ambassador to the United States to prevent him from seizing power. The attempted coup reached a stalemate, and although the trio did not take power, a group of officers led by General Nguyễn Chánh Thi and Air Marshal Nguyễn Cao Kỳ, and hostile to both the plot and to Khánh himself, were able to force a leadership change and take control themselves with the support of American officials, who had lost confidence in Khánh.

Although Khánh had seized power in January 1964 in alliance with Khiêm, the pair had soon fallen out over policy disputes along religious lines, and the Catholic Khiêm began to plot against Khánh. Khiêm was believed to have helped plan a failed coup in September 1964, and Khánh exiled him as a result. While in Washington, Khiêm continued to plot alongside his aide Thảo, who was actually a communist agent bent on trying to foment infighting at every opportunity. Aware of Thảo's plans, Khánh summoned him back to Vietnam in an apparent attempt to capture him, and Thảo responded by going into hiding and preparing for his attack. In the meantime, Khánh's hold on power was slipping as his military support dwindled, and he became increasingly reliant on the support of civilian Buddhist activists who favored negotiations with the communists and opposed escalation of the Vietnam War. The Americans—most notably Ambassador Maxwell Taylor—were opposed to this and had been lobbying various senior Vietnamese officers such as Kỳ to overthrow Khánh, who knew that American-sponsored moves to depose him were afoot.

However, the Americans were not counting on Thảo and his fellow Catholic Phát trying to seize power on an explicitly religious platform, claiming fidelity to assassinated former Catholic President Ngô Đình Diệm and promising to recall Khiêm from the US to lead the new regime.