North Vietnam’s air force dates back to March 1956 when the first group of airmen were sent to China and the Soviet Union for training.  A number of small airfields were constructed in North Vietnam and transport aircraft and trainers were acquired from communist sources.  In 1960 a total of 52 pilots were sent to China to learn to fly the MiG-15/17.  Progress was slow and it was not until 3 February 1964 that the 921st Fighter Regiment of the Vietnamese People’s Air Force was formed at Mong Tu air base in China.  The Regiment was equipped initially with 36 MiG-17s donated by the Soviet Union.  Meanwhile construction of the first jet-capable airfield was progressing at Yen Bai northwest of Hanoi.  The base was substantially complete by mid-1964 but the Regiment remained in China where it continued to train until the Gulf of Tonkin Incident.  On 6 August 1964 the first group of MiGs flew from China to Yen Bai where they commenced preparations to defend their homeland.  The training was methodical and thorough and concentrated on the use of a network of ground controlled interception radars that was being built in North Vietnam.  The tactics adopted recognised the strengths and weaknesses of the MiG-17 compared to its American adversaries and these tactics were later modified with experience.  The MiG force was held back until the Rolling Thunder strikes began to reach the 20th parallel.  On 3 April the 921st Fighter Regiment made its first operational sorties against the US Navy strike force which attacked the Thanh Hoa bridges.  The North Vietnamese claimed two F-8 Crusaders destroyed during this engagement although, in fact, only one F-8 was damaged.  The following day saw the VPAF’s first real victories when two F-105s were shot down although this was achieved for the loss of three of the MiGs and their pilots.  Five more MiGs were shot down in June and July and others lost in accidents with the result that the MiGs were virtually stood down for nine months of retraining, not being seen in numbers again until April 1966.  Meanwhile the 921st had been joined by the 923rd Fighter Regiment which was formed at Kep airfield northeast of Hanoi on 7 September 1965.  In November of the same year the MiG-17s were joined by the first of the more capable MiG-21s.  The MiG-21 was equipped with two K-13 air-to-air missiles, designated the AA-2 Atoll by NATO.  The first reported sighting of a MiG-21 took place on 15 January 1966 and the aircraft often operated in conjunction with the MiG-17s.  By the end of 1965 the VPAF had about 75 MiGs together with eight Il-28 jet bombers in service.  To counter the MiG threat the USAF introduced Big Eye (later College Eye) EC-121D detachments from the 552nd AEW&C Wing based at various airfields from 17 April 1965.  Ships of TF 77 also provided radar coverage and MiG warnings for US aircraft operating over North Vietnam.