▁China ▁impossible . ▁ ▁Many ▁of ▁the ▁supplies ▁had ▁to ▁be ▁delivered ▁to ▁China ▁by ▁the ▁B - 2 9 s ▁themselves . ▁For ▁this ▁role , ▁they ▁were ▁stri pped ▁of ▁nearly ▁all ▁combat ▁equipment ▁and ▁used ▁as ▁flying ▁tank ers ▁and ▁each ▁carried ▁seven ▁tons ▁of ▁fuel ▁for ▁the ▁six - hour ▁( one ▁way ) ▁flight , ▁which ▁itself ▁was ▁almost ▁at ▁the ▁limit ▁of ▁the ▁B - 2 9 ' s ▁range . ▁The ▁H ump ▁route ▁was ▁so ▁dangerous ▁and ▁difficult ▁that ▁each ▁time ▁a ▁B - 2 9 ▁fle w ▁from ▁India ▁to ▁China ▁it ▁was ▁counted ▁as ▁a ▁combat ▁mission . ▁ ▁It ▁took ▁six ▁round - tri p ▁fl ights ▁by ▁each ▁Super fort ress ▁to ▁K w ang han ▁in ▁order ▁to ▁mount ▁one ▁combat ▁mission ▁from ▁the ▁forward ▁base . ▁ ▁The ▁first ▁combat ▁mission ▁by ▁the ▁group ▁took ▁place ▁on ▁June ▁ 5 , ▁ 1 9 4 4 ▁when ▁squad rons ▁of ▁the ▁ 4 0 th ▁took ▁off ▁from ▁India ▁to ▁attack ▁the ▁Mak as an ▁rail road ▁yards ▁at ▁Bang k ok , ▁Th ailand . ▁This ▁involved ▁a ▁ 2 2 6 1 - mile ▁round ▁trip , ▁the ▁longest ▁bomb ing ▁mission ▁yet ▁attempted ▁during ▁the ▁war . ▁ ▁On ▁June ▁ 1 5 ▁the ▁group ▁participated ▁in ▁the ▁first ▁American ▁Air ▁Force ▁attack ▁on ▁the ▁Japanese ▁Home ▁Islands ▁since ▁the ▁D ool ittle ▁ra id ▁in ▁ 1 9 4 2 . ▁Oper ating ▁from ▁bases