Sentence:  While engaged in building a “<WSD>scance</WSD>” (an erection of stones in crescent formation to afford cover), amid the constant sniping of the enemy, and while in a stooping position a Mauser bullet struck him under the left eye at the infra-orbital foramen, passing through the antrum and making its exit drove before it the the second bicuspid tooth, splitting the first bicuspid. 
Meaning of the word marked with <WSD> tags:  A crescent-shaped structure of stones built to afford cover in battle.