▁a ▁sie ge ▁even ▁before ▁reaching ▁the ▁for tr ess . ▁Their ▁modern ▁success ors ▁include ▁the ▁bar bed ▁wire ▁used ▁in ▁both ▁world ▁wars . ▁ ▁The ▁route ▁of ▁many ▁simple ▁land wehr s ▁shows , ▁according ▁to ▁new ▁research , ▁that ▁they ▁were ▁completely ▁un su itable ▁for ▁defence ▁purposes ▁in ▁many ▁places . ▁From ▁this ▁it ▁can ▁be ▁concluded ▁that ▁some ▁of ▁these ▁install ations ▁were ▁mainly ▁used ▁for ▁border ▁mark ing ▁and ▁collect ing ▁custom s ▁duties . ▁They ▁never theless ▁restricted ▁the ▁free ▁mob ility ▁of ▁enemy ▁troops , ▁so ▁that ▁they ▁were ▁certainly ▁of ▁some ▁military ▁utility . ▁For ▁example , ▁the ▁Stad th agen ▁around ▁War endorf ▁in ▁the ▁Th irty ▁Years ' ▁War ▁succeeded ▁in ▁protect ing ▁the ▁town . ▁Although ▁the ▁enemy ▁did ▁in ▁fact ▁break ▁into ▁the ▁municipal ▁territory , ▁they ▁did ▁not ▁risk ▁a ▁major ▁attack ▁simply ▁because ▁of ▁the ▁danger , ▁in ▁a ▁counter - att ack , ▁of ▁not ▁being ▁able ▁to ▁beat ▁a ▁retre at ▁quickly ▁enough ▁through ▁the ▁narrow ▁bre ach ▁in ▁the ▁land wehr . ▁ ▁As ▁a ▁border ▁fort ification ▁around ▁areas ▁that ▁had ▁been ▁given ▁specific ▁rights , ▁land wehr s ▁had ▁g aps ▁ ▁in ▁some ▁places ▁for ▁roads , ▁for ▁counter - att ack ▁routes ▁or ▁for ▁trade . ▁These ▁g aps ▁( called ▁Schl ags ) ▁were ▁guard ed ▁by ▁simple ▁to ll g ates , ▁by ▁side ▁roads ▁( so - called ▁Sch lingen )), ▁or ▁- ▁by ▁means ▁of ▁to