In June 1965, when Kỳ became prime minister of South Vietnam, he promoted Loan to colonel and appointed him director of the Military Security Service. This was followed within a few months by an appointment to director of the Central Intelligence Organization, giving Loan simultaneous control of both military intelligence and security. He was further made director general of the Republic of Vietnam National Police in April 1966. Holding these positions enabled Loan to wield immense power, and he supervised the suppression of the early 1966 uprising of Kỳ's rival General Nguyễn Chánh Thi and dissident Buddhists. When Kỳ agreed to become vice president to Nguyễn Văn Thiệu in 1967, the former relied on the support Loan provided for him in order to retain power.