AC-47 Spooky gunships of the newly-activated 14th Air Commando Squadron. On 31 January 1968 at the start of the Tet Offensive, naval gunfire from was used to deter a VC attack on the base and gunfire from the later deterred a similar attack. On 15 April 1968 the 550-man 821st Combat Security Police Squadron was deployed to the base on temporary duty, they were replaced by the 822nd Combat Security Police Squadron in August 1968. The 822nd was replaced by the 823rd Combat Security Police Squadron in March 1969 and was then replaced by the 821st in August 1969. The 821st remained at Phan Rang until February 1971 when it was inactivated. In mid-September 1968 the Federalized Utah National Guard 116th Engineer Combat Battalion deployed to Phan Rang Air Base to begin a ten-month tour of duty. Between 10 August 1968 and 31 May 1969, the 554th Civil Engineering Squadron built an armament and electronics shop, fire station, a concrete access taxiway, 6 troop barracks and 2 officers quarters protecting by a revetment wall, a 49,000-square-yard asphalt hardstand, and a base theater. Commencing in October 1968, USAF engineers built 61 "Wonderarch" aircraft shelters at Phan Rang. On 3 May 1970 VC sappers attacked the base but were repulsed with minor damage and no Allied casualties. On 10 September VC attacked the main gate but were also repulsed with little damage and no Allied casualties. 315th Air Commando Wing/Special Operations Wing The 315th Air Commando Wing (Troop Carrier) moved to Phan Rang from Tan Son Nhut Air Base on 15 June 1967 and became a tenant unit supported by the 35th Combat Support Group.Initially designated as the 315th Air Commando Wing, it was redesignated the 315th Special Operations Wing on 1 August 1968. Squadrons assigned were: 12th Special Operations Squadron: 15 June 1967 – 30 September 1970 (C-123B/K) 19th Special Operations Squadron: 15 June 1967 – 30 June 1971 (C-123B/K Tail Code: WE) 309th Special Operations Squadron: 15 June 1967 – 31 July 1970 (C-123B/K Tail Code: WH) 310th Special Operations Squadron: 15 June 1967 – 15 January 1972 (C-123B/K Tail Code: WM) 311th Special Operations Squadron: 15 June 1967 – 15 October 1971 (C-123B/K Tail Code: WV) Operations included aerial movement of troops and cargo, flare drops, aeromedical evacuation, and air-drops of critical supplies and paratroops. In 1971–1972 the unit helped to train C-123 aircrews for the RVNAF. The wing