▁teams ▁of ▁men ▁who ▁would ▁black ▁up ▁their ▁faces ▁with ▁bur nt ▁c ork ▁before ▁crossing ▁the ▁bar bed ▁wire ▁and ▁other ▁de br is ▁of ▁no ▁man ' s ▁land ▁to ▁in fil tr ate ▁enemy ▁tren ch ▁systems . ▁The ▁distance ▁between ▁friendly ▁and ▁enemy ▁front ▁lines ▁varied , ▁but ▁was ▁generally ▁several ▁hundred ▁metres . ▁Any ▁attempt ▁to ▁ra id ▁a ▁tren ch ▁during ▁day light ▁hours ▁would ▁have ▁been ▁point less ▁because ▁it ▁would ▁have ▁been ▁quickly ▁sp otted : ▁enemy ▁machine ▁g unn ers ▁and ▁sn ip ers ▁had ▁a ▁clear ▁view ▁of ▁no ▁man ' s ▁land ▁and ▁could ▁easily ▁shoot ▁anyone ▁who ▁showed ▁their ▁head ▁above ▁the ▁tren ch ▁par ap et . ▁ ▁Standard ▁practice ▁was ▁to ▁cre ep ▁slowly ▁up ▁on ▁the ▁sent ries ▁guard ing ▁a ▁small ▁sector ▁of ▁an ▁enemy ▁front ▁line ▁tren ch ▁( looking ▁for ▁the ▁g low ▁of ▁c igare tt es ▁in ▁the ▁dark ▁or ▁listening ▁for ▁convers ations ) ▁then ▁kill ▁them ▁as ▁quietly ▁as ▁possible . ▁Having ▁secured ▁the ▁tren ch ▁the ▁ra iders ▁would ▁complete ▁their ▁mission ▁object ives ▁as ▁quickly ▁as ▁possible , ▁ide ally ▁within ▁several ▁minutes . ▁Ra iders ▁were ▁aware ▁that ▁the ▁longer ▁they ▁stayed ▁in ▁the ▁tren ch , ▁the ▁greater ▁the ▁lik elihood ▁of ▁enemy ▁rein for c ements ▁arriv ing . ▁Gren ades ▁would ▁be ▁thrown ▁into ▁d ug outs ▁where ▁enemy ▁troops ▁were ▁sleep ing ▁before ▁the ▁ra iders ▁left ▁the ▁enemy ▁lines ▁to ▁return ▁to ▁their