many sandbags of a trench dug in the ground to defend army soldiers from enemy raids

army bags barricade battlefield communication trench conflict defence defense dig digging ditch dug dugout enemy entrench oneself entrenched entrenchment excavating excavation first world war fortification foxhole great ground gunny sack hessian bag jute military protection raids sacking sandbag sandbags security shelter soldierly soldiers strategy trenches trenching warfare ww1 wwi