▁ 1 9 1 5 , ▁defining ▁a ▁theory ▁of ▁def ensive ▁war fare ▁to ▁be ▁used ▁on ▁the ▁Western ▁Front , ▁intended ▁to ▁enable ▁ground ▁to ▁be ▁held ▁with ▁the ▁few est ▁possible ▁troops . ▁By ▁econom ising ▁on ▁man power ▁in ▁the ▁west , ▁a ▁larger ▁number ▁of ▁divisions ▁could ▁be ▁sent ▁to ▁the ▁Eastern ▁Front . ▁The ▁front ▁line ▁was ▁to ▁be ▁fort ified ▁to ▁enable ▁its ▁defence ▁with ▁small ▁numbers ▁of ▁troops ▁in def initely ▁and ▁captured ▁ground ▁was ▁to ▁be ▁recovered ▁by ▁counter - att acks . ▁A ▁second ▁tren ch ▁was ▁to ▁be ▁d ug ▁behind ▁the ▁front ▁line , ▁to ▁shelter ▁the ▁tren ch ▁g arrison ▁and ▁to ▁have ▁easy ▁access ▁to ▁the ▁front ▁line , ▁through ▁covered ▁communication ▁tren ches . ▁Should ▁counter - att acks ▁fail ▁to ▁recover ▁the ▁front ▁tren ch , ▁a ▁rear ward ▁line ▁was ▁to ▁be ▁connected ▁to ▁the ▁remaining ▁parts ▁of ▁the ▁front ▁line , ▁limit ing ▁the ▁loss ▁of ▁ground ▁to ▁a ▁b end ▁() ▁in ▁the ▁line , ▁rather ▁than ▁a ▁break through . ▁The ▁building ▁of ▁the ▁new ▁def ences ▁took ▁until ▁the ▁aut umn ▁of ▁ 1 9 1 5 ▁and ▁confront ed ▁Franco - B rit ish ▁off ens ives ▁with ▁an ▁evol ving ▁system ▁of ▁field ▁fort ifications , ▁which ▁was ▁able ▁to ▁abs orb ▁the ▁increasing ▁power ▁and ▁s oph istic ation ▁of ▁break through ▁attempts . ▁ ▁During ▁the ▁mobile ▁operations ▁of ▁ 1 9 1 4 , ▁arm ies ▁operating