Sentence:  This description of the old front line, as it was when the Battle of the Somme began, may some day be of use....It is hoped that this description of the <WSD>line</WSD> will be followed by an account of our people's share in the battle. 
Meaning of the word marked with <WSD> tags:  A trench or rampart, or the non-physical demarcation of the extent of the territory occupied by specified forces.