Editing Operation Linebacker II (section)

===Vietnamese air defense===
At the start of Linebacker II, the air defense missile forces of the Vietnamese People's Army had 36 air defense missile battalions armed with the S-75M Dvina ([[SA-2 Guideline]]) missile system; probably half were involved in this operation.<ref>Patterns and Predictability: The Soviet Evaluation of Operation Linebacker II, by Dana Drenkowski and Lester W. Grau. p. 17</ref> The SA-2 system was first fielded in 1957 and was a fairly obsolete and cumbersome system by 1972 standards.<ref>Patterns and Predictability: The Soviet Evaluation of Operation Linebacker II, by Dana Drenkowski and Lester W. Grau. p. 35</ref> The [[VPAF]] had only 71 operational aircraft. Of these, only 47 aircraft (31 [[MiG-21]]s and 16 [[MiG-17]]s) could be used for air combat. The MiG-19s were made in China and were not used in combat. Only 13 MiG-21 pilots and five MiG-17 pilots were trained for individual night flight in normal and flying in difficult meteorological conditions. Of 194 pilots, 75 (about 40 percent) were young.{{Elaborate|reason='Young' is meaningless. please elaborate this.|date=August 2022}}<ref name="Predictability p. 26"/>