The 81st Ranger Group was a unique special unit of the Vietnamese Rangers of the Southern Army of the Republic of Vietnam. It was originally formed as part of the Project DELTA reaction force. Formed on 1 November 1964 as the 91st Airborne Ranger Battalion and consisted of three companies of Montagnards. A fourth company was added in 1965. It was reorganized in 1966 as the 81st Ranger Battalion by the "purging of non-Vietnamese" to make it more "effective". The 81st consisted of six all-Vietnamese companies. It was officially under LLDB command and not that of Ranger Command. It was actually under the direct control of Project DELTA although two companies were made available to the LLDB. Its primary mission was to provide airmobile reaction forces to aid in the extraction of recon teams and execute immediate exploitation raids on targets discovered by the teams. It was also used to reinforce SF camps under siege. During and after Tet it also fought in Saigon and handled urban fighting conditions quite well. The 81st Ranger Battalion was later expanded to seven companies and renamed the 81st Ranger Group which was facilitated by the merger of Delta Teams with the existing three Ranger Companies. The entire unit was parachute trained and was under the direct control of the ARVN G-2. In 1975 it was headquartered at Trang Lon, Tay Linh, and consisted of a Headquarters, seven Ranger and one Pathfinder company. Group strength varied from 920 to 1200 men. The 91st/81st battalion continued to wear the old LLDB Green Beret instead of the Ranger Brown/Maroon Beret.
During the 1975 final collapse of the South,, elements of the group were present at the final fall of Tan Son NhutAir Base. The 3rd Task Force, 81st Ranger Group commanded by Maj. Pham Chau Tai defended Tan Son Nhut and they were joined by the remnants of the Loi Ho unit. At 07:15 on 30 April the PAVN 24th Regiment approached the Bay Hien intersection, a kilometre and a half from the base's main gate. The lead T-54 was hit by M67 recoilless rifle fire, and then the next T-54 was hit by a shell from an M48 tank. The PAVN infantry moved forward and engaged the ARVN in house to house fighting forcing them to withdraw to the base by 08:45. The PAVN then sent three tanks and an infantry battalion to assault the main gate and they were met by intensive anti-tank and machine gun fire knocking out the 3 tanks and killing at least 20 PAVN soldiers. The PAVN tried to bring forward an 85mm antiaircraft gun but the ARVN knocked it out before it could start firing. The PAVN 10th Division ordered 8 more tanks and another infantry battalion to join the attack, but as they approached the Bay Hien intersection they were hit by an airstrike from RVNAF jets operating from Binh Thuy Air Base which destroyed two T-54s. The six surviving tanks arrived at the main gate at 10:00 and began their attack, with 2 being knocked out by antitank fire in front of the gate and another destroyed as it attempted a flanking manoeuvre. At approximately 10:30 Maj. Pham heard of the surrender broadcast of President Dương Văn Minh and went to the ARVN Joint General Staff Compound to seek instructions. He called General Minh, who told him to prepare to surrender, Pham reportedly told Minh "If Viet Cong tanks are entering Independence Palace we will come down there to rescue you sir." Minh refused Pham's suggestion and Pham then told his men to withdraw from the base gates. At 11:30 the PAVN entered the base.
