▁September ▁ 1 7 , ▁McC ook ' s ▁corps ▁had ▁reached ▁Stevens ▁G ap ▁and ▁the ▁three ▁Union ▁corps ▁were ▁now ▁much ▁less ▁vulner able ▁to ▁individual ▁defeat . ▁Yet ▁B rag g ▁decided ▁that ▁he ▁still ▁had ▁an ▁opportunity . ▁Rein for ced ▁with ▁two ▁divisions ▁arriv ing ▁from ▁Virginia ▁under ▁L t . ▁Gen . ▁James ▁Long street , ▁and ▁a ▁division ▁from ▁Mississippi ▁under ▁Brig . ▁Gen . ▁Bush rod ▁R . ▁Johnson , ▁he ▁decided ▁to ▁move ▁his ▁army ▁north ward ▁on ▁the ▁morning ▁of ▁September ▁ 1 8 ▁and ▁advance ▁toward ▁Ch att ano oga , ▁forcing ▁Rose cr ans ' s ▁army ▁out ▁to ▁fight ▁or ▁to ▁withdraw . ▁If ▁Rose cr ans ▁fought , ▁he ▁risk ed ▁being ▁driven ▁back ▁into ▁Mc L em ore ' s ▁C ove . ▁The ▁Confeder ate ▁army ▁was ▁to ▁move ▁beyond ▁the ▁Federal ▁left ▁fl ank ▁at ▁Lee ▁and ▁Gordon ' s ▁Mill ▁and ▁then ▁cross ▁West ▁Ch ick am aug a ▁Creek . ▁He ▁specified ▁four ▁crossing ▁points , ▁from ▁north ▁to ▁south : ▁Johnson ' s ▁division ▁at ▁Re ed ' s ▁Bridge , ▁Walker ' s ▁Reserve ▁Corps ▁at ▁Alexander ' s ▁Bridge , ▁Buck ner ' s ▁corps ▁at ▁Th ed ford ' s ▁Ford , ▁and ▁Pol k ' s ▁corps ▁at ▁Dal ton ' s ▁Ford . ▁Hill ' s ▁corps ▁would ▁anchor ▁the ▁army ' s ▁left ▁fl ank ▁and ▁the ▁caval ry ▁under ▁For rest ▁and ▁Whe eler ▁would ▁cover