RVNAF, older C-123s were returned to the USAF for disposal. As the buildup of the RVNAF continued, the success of the Vietnamization program was evident during the 1972 Easter Offensive. Responding to the People's Army of Vietnam (PAVN) attack, the RVNAF flew more than 20,000 strike sorties which helped to stem the advance. In the first month of the offensive, transports from Tan Son Nhut ferried thousands of troops and delivered nearly 4,000 tons of supplies throughout the country. The offensive also resulted in additional deliveries of aircraft to the RVNAF under Operation Enhance. Also, fighter aircraft arrived at Tan Son Nhut for the first time in the F-5A/B Freedom Fighter and the F-5E Tiger II. The F-5s were subsequently transferred to Bien Hoa and Da Nang ABs. 1973 Ceasefire The Paris Peace Accords of 1973 brought an end to the United States advisory capacity in South Vietnam. In its place, as part of the agreement, the Americans retained a Defense Attaché Office (DAO) at Tan Son Nhut Airport, with small field offices at other facilities around the country. The technical assistance provided by the personnel of the DAOs and by civilian contractors was essential to the RVNAF, however, because of the cease-fire agreement, the South Vietnamese could not be advised in any way on military operations, tactics or techniques of employment. It was through the DAO that the American/South Vietnamese relationship was maintained, and it was primarily from this source that information from within South Vietnam was obtained. The RVNAF provided statistics with regards to the military capability of their units to the DAO, however the information was not always reliable. From the Easter Offensive of 1972, it was clear that without United States aid, especially air support, the ARVN would not be able to defend itself against continuing PAVN attacks. This was demonstrated at the fighting around Pleiku, An Lộc and Quảng Trị where the ARVN would have been defeated without continuous air support, mainly supplied by the USAF. The ARVN relied heavily on air support, and with the absence of the USAF, full responsibility fell on the RVNAF alone. Although equipped with large numbers of Cessna A-37 Dragonfly and F-5 attack aircraft to carry out close air support, during the 1972 offensive, heavy bombardment duty was left to USAF aircraft. As part of the Paris Peace Accords, a Joint Military Commission was established and VC/PAVN troops were