▁enable ▁more ▁divisions ▁to ▁be ▁sent ▁to ▁the ▁Eastern ▁Front . ▁New ▁def ences ▁were ▁to ▁be ▁built ▁behind ▁the ▁front ▁line ▁to ▁contain ▁a ▁break through ▁until ▁the ▁position ▁was ▁restored ▁by ▁counter - att acks . ▁The ▁ ▁began ▁the ▁huge ▁task ▁of ▁building ▁field ▁fort ifications , ▁which ▁were ▁not ▁complete ▁until ▁the ▁aut umn ▁of ▁ 1 9 1 5 . ▁ ▁Background ▁ ▁Str ateg ic ▁develop ments ▁ ▁Plan ▁XVII ▁ ▁Under ▁Plan ▁XVII ▁the ▁French ▁pe ac etime ▁army ▁was ▁to ▁form ▁five ▁field ▁arm ies , ▁with ▁groups ▁of ▁Reserve ▁divisions ▁attached ▁and ▁a ▁group ▁of ▁reserve ▁divisions ▁was ▁to ▁assemble ▁on ▁each ▁fl ank , ▁ ▁The ▁arm ies ▁were ▁to ▁concent rate ▁opposite ▁the ▁German ▁front ier ▁around ▁É p inal , ▁Nancy ▁and ▁Verd un – Char lev ille - Me zi ères , ▁with ▁an ▁army ▁in ▁reserve ▁around ▁Sainte - M ene h ould ▁and ▁Com mer cy . ▁Since ▁ 1 8 7 1 ▁railway ▁building ▁had ▁given ▁the ▁French ▁General ▁staff ▁six teen ▁lines ▁to ▁the ▁German ▁front ier ▁against ▁th ir teen ▁available ▁to ▁the ▁German ▁army ▁and ▁the ▁French ▁could ▁wait ▁until ▁German ▁intent ions ▁were ▁clear . ▁The ▁French ▁deployment ▁was ▁intended ▁to ▁be ▁ready ▁for ▁a ▁German ▁off ensive ▁in ▁Lor raine ▁or ▁through ▁Belg ium . ▁It ▁was ▁anticip ated ▁that ▁the ▁Germ ans ▁would ▁use ▁reserve ▁troops ▁but ▁also ▁expected ▁that ▁a ▁large ▁German ▁army ▁would ▁be ▁mobil ised ▁on ▁the ▁border