In 1958, he graduated from the Command and General Staff College, [Fort Leavenworth], Kansas. He served in the Army of the Republic of Vietnam (ARVN) and rose to the rank of Lieutenant General, Chief of Staff Inter-armed Forces (Tham Muu truong Lien Quan). He participated in many military cabinets between 1965 and 1974 during the various military junta's leadership after the deposal of President Ngo Dinh Diem. Was Political Commissar in the Armed Forces Council (Uy Vien Chinh Tri Hoi Dong Quan Luc), Head of the Central Intelligence Directorate (Phu Dac Uy Trung Uong Tinh Bao), Minister of Information (Tong Truong Thong Tin), Minister of National Security (Tong Truong An Ninh Quoc Gia), and also Interior Minister (Tong Truong Noi Vu) for a short time.