 Following the withdrawal of the French, the VNA became the ARVN and Thiệu was the head of the Vietnamese National Military Academy for four years before becoming a division commander and colonel.In November 1960, he helped put down a coup attempt against President Ngô Đình Diệm.During this time, he also converted to Roman Catholicism and joined the regime's secret Cần Lao Party; Diệm was thought to give preferential treatment to his co-religionists and Thiệu was accused of being one of many who converted for political advancement.