▁Grand ▁Cour onn é ▁( 4 – 1 3 ▁September ) ▁began ▁next ▁day , ▁when ▁the ▁German ▁ 7 th ▁and ▁ 6 th ▁Arm ies ▁attacked ▁simultaneously ▁at ▁St . ▁Di é ▁and ▁Nancy , ▁as ▁the ▁Second ▁Army ▁sent ▁rein for c ements ▁to ▁the ▁Third ▁Army . ▁Cost ly ▁fighting ▁continued ▁until ▁ 1 2 ▁September ▁but ▁the ▁French ▁were ▁able ▁to ▁withdraw ▁more ▁than ▁four ▁corps ▁to ▁rein force ▁the ▁arm ies ▁on ▁the ▁left ▁fl ank . ▁On ▁ 1 3 ▁September , ▁Pont - à - M ous son ▁and ▁L un é ville ▁were ▁re capt ured ▁by ▁the ▁French ▁and ▁the ▁advance ▁continued ▁close ▁to ▁the ▁Se ille ▁river , ▁where ▁the ▁front ▁stabil ised . ▁The ▁batt les ▁kept ▁a ▁large ▁number ▁of ▁German ▁troops ▁in ▁Lor raine , ▁as ▁the ▁Great ▁Ret re at ▁further ▁west ▁cul min ated ▁on ▁the ▁Mar ne . ▁ ▁The ▁Great ▁Ret re at , ▁ 2 4 ▁August ▁– ▁ 5 ▁September ▁ ▁The ▁French ▁Fif th ▁Army ▁fell ▁back ▁about ▁ ▁from ▁the ▁Sam bre ▁during ▁the ▁Battle ▁of ▁Char ler oi ▁( 2 2 ▁August ) ▁and ▁began ▁a ▁greater ▁withdraw al ▁from ▁the ▁area ▁south ▁of ▁the ▁Sam bre ▁on ▁ 2 3 ▁August . ▁The ▁BE F ▁fought ▁the ▁Battle ▁of ▁M ons ▁on ▁ 2 4 ▁August , ▁by ▁when ▁the ▁French ▁First ▁and ▁Second ▁arm ies ▁had ▁been ▁pushed ▁back ▁by ▁attacks ▁of ▁the ▁German ▁ 7 th ▁and