. ▁ ▁Following ▁their ▁defeat ▁at ▁the ▁hands ▁of ▁the ▁North ▁Vietnam ese ▁Air ▁Force , ▁Colonel ▁Robin ▁Old s ▁learned ▁that ▁Se vent h ▁Air ▁Force ▁intelligence ▁had ▁watched ▁North ▁Vietnam ese ▁Mi G ▁f igh ters ▁pract icing ▁their ▁new ▁tact ics ▁for ▁ten ▁days ▁prior ▁to ▁the ▁battle ▁of ▁ 2 3 ▁August , ▁but ▁had ▁not ▁passed ▁that ▁information ▁on ▁to ▁the ▁ 8 th ▁T act ical ▁F ighter ▁Wing ▁and ▁other ▁units . ▁Thus , ▁it ▁soon ▁became ▁clear ▁to ▁U . S ▁command ers ▁that ▁the ▁reason ▁the ▁North ▁Vietnam ese ▁repeatedly ▁stood ▁down ▁their ▁f ighter ▁force ▁was ▁because ▁they ▁were ▁working ▁on ▁their ▁new ▁t actic . ▁In ▁the ▁first ▁half ▁of ▁ 1 9 6 7 , ▁the ▁North ▁Vietnam ese ▁had ▁realized ▁they ▁could ▁not ▁directly ▁confront ▁U . S . ▁f igh ters ▁in ▁air - to - air ▁combat , ▁so ▁they ▁changed ▁their ▁procedures ▁for ▁the ▁deployment ▁of ▁their ▁numer ically ▁inferior ▁Mi G ▁units . ▁To ▁take ▁advantage ▁of ▁the ▁Mi G - 2 1 ' s ▁speed ▁and ▁small ▁size , ▁pil ots ▁flying ▁the ▁type ▁were ▁instruct ed ▁to ▁intercept ▁targets ▁only ▁at ▁high ▁speed ▁behind ▁or ▁above ▁U . S . ▁strike ▁form ations . ▁ ▁Then , ▁as ▁they ▁approached ▁their ▁target , ▁the ▁Mi G - 2 1 ▁pil ots ▁would ▁make ▁a ▁su person ic ▁div ing ▁pass ▁against ▁trailing ▁or ▁isolated ▁fl ights , ▁so ▁they ▁could ▁position ▁themselves ▁for ▁a