▁September ▁ ▁The ▁French ▁Six th ▁Army ▁began ▁to ▁advance ▁along ▁the ▁O ise , ▁west ▁of ▁Com pi èg ne ▁on ▁ 1 7 ▁September . ▁French ▁reconna issance ▁aircraft ▁were ▁ground ed ▁during ▁bad ▁weather ▁and ▁caval ry ▁were ▁exha usted , ▁which ▁dep riv ed ▁the ▁French ▁command ers ▁of ▁information . ▁As ▁news ▁reached ▁J off re ▁that ▁two ▁German ▁corps ▁were ▁moving ▁south ▁from ▁Ant werp , ▁the ▁Six th ▁Army ▁was ▁forced ▁to ▁end ▁its ▁advance ▁and ▁dig ▁in ▁around ▁N amp cel ▁and ▁Ro ye . ▁The ▁IV ▁and ▁XIII ▁corps ▁were ▁transferred ▁to ▁the ▁Second ▁Army , ▁along ▁with ▁the ▁ 1 st , ▁ 5 th , ▁ 8 th ▁and ▁ 1 0 th ▁Caval ry ▁divisions ▁of ▁the ▁Caval ry ▁Corps ▁( General ▁Louis ▁Con ne au ), ▁the ▁XIV ▁and ▁XX ▁Corps ▁were ▁with dra wn ▁from ▁the ▁First ▁and ▁the ▁original ▁Second ▁Army ▁to ▁assemble ▁south ▁of ▁Am iens , ▁with ▁a ▁screen ▁of ▁the ▁ 8 1 st , ▁ 8 2 nd , ▁ 8 4 th ▁and ▁ 8 8 th ▁Territ orial ▁divisions , ▁to ▁protect ▁French ▁communic ations . ▁The ▁French ▁advanced ▁on ▁ 2 2 ▁September , ▁on ▁a ▁line ▁from ▁L assign y ▁north wards ▁to ▁Ro ye ▁and ▁Cha ul nes ▁around ▁the ▁German ▁fl ank ▁but ▁met ▁the ▁German ▁II ▁Corps , ▁which ▁had ▁arrived ▁on ▁the ▁night ▁of ▁▁ ▁on ▁the ▁right ▁fl ank ▁of ▁the ▁IX ▁Reserve ▁Corps .