If sides had to build 1000s of miles of trenches, it would require many stones. The type of rapid fire weaponry that the manufacturers produced made WW1 perfectly suited for defensive weapons. Old generals like Haig could not grasp the change, and he was rightfully called a butcher. He somewhat redeemed himself later when tanks joined the battle. All of those defensive positions needed massive engineering and construction efforts. This shot beautifully captures one of the millions of small yet difficult efforts to make the war machine go.