On 26 October 1955 , the military was reorganized by the administration of President Ngô Đình Diệm who then formally established the Army of the Republic of Vietnam ( ARVN ) on 30 December 1955 . The air force was established as a separate service known as the Republic of Vietnam Air Force ( RVNAF ) . Early on , the focus of the army was the guerrilla fighters of the Viet Cong ( VC ) , formed to oppose the Diệm administration . The United States , under President John F. Kennedy sent advisors and a great deal of financial support to aid the ARVN in combating the insurgents . A major campaign , developed by Ngô Đình Nhu and later resurrected under another name was the " Strategic Hamlet Program " which was regarded as unsuccessful by Western media because it was " inhumane " to move villagers from the countryside to fortified villages . ARVN leaders and President Diệm were criticized by the foreign press when the troops were used to crush armed anti-government religious groups like the Cao Đài and Hòa Hảo as well as to raid Buddhist temples , which according to Diệm , were harboring VC guerrillas . The most notorious of these attacks occurred on the night of August 21 , 1963 , during the Xá Lợi Pagoda raids conducted by the Special Forces , which caused a death toll estimated to range into the hundreds
Xá Lợi Pagoda raids
Xá Lợi Pagoda raids
Army of the Republic of Vietnam