s ▁capital ▁with ▁H ai ▁Ph ong . ▁To ▁minim ize ▁the ▁effects ▁of ▁U . S . ▁strik es , ▁North ▁Vietnam ese ▁authorities ▁constructed ▁several ▁alternate ▁rail ▁yards ▁on ▁the ▁north - e astern ▁train ▁line , ▁including ▁the ▁Y en ▁Vien ▁rail ▁yard ▁which ▁located ▁ ▁north ▁of ▁H ano i ▁and ▁ran ▁through ▁Th ai ▁N gu yen , ▁and ▁linked ▁up ▁with ▁the ▁main ▁line ▁at ▁K ep ▁close ▁to ▁China . ▁ ▁In ▁response , ▁the ▁Se vent h ▁Air ▁Force ▁launched ▁repeated ▁strik es ▁on ▁the ▁Y en ▁Vien ▁rail ▁yard ▁and ▁other ▁infrastr uct ures ▁which ▁linked ▁H ano i ▁with ▁the ▁China ▁buffer ▁zone . ▁On ▁ 2 1 ▁August ▁ 1 9 6 7 , ▁a ▁formation ▁of ▁twenty ▁F - 1 0 5 ▁Th under ch ief s ▁and ▁eight ▁F - 4 ▁Ph ant oms ▁ra ided ▁Y en ▁Vien , ▁which ▁contained ▁about ▁ 1 5 0 ▁box c ars . ▁The ▁Americans ▁claimed ▁to ▁have ▁dam aged ▁more ▁than ▁half ▁of ▁the ▁box c ars ▁and ▁tra pped ▁the ▁remainder ▁in ▁the ▁rail ▁yard , ▁so ▁they ▁returned ▁two ▁days ▁later ▁to ▁destroy ▁the ▁rest . ▁On ▁the ▁afternoon ▁of ▁ 2 3 ▁August ▁ 1 9 6 7 , ▁a ▁flight ▁of ▁six teen ▁F - 4 s ▁from ▁the ▁ 8 th ▁T act ical ▁F ighter ▁Wing ▁esc orted ▁a ▁formation ▁of ▁thirty - six ▁F - 1 0 5 ▁strike ▁aircraft ▁from ▁the ▁ 3