In this photograph . . . soldiers are shown digging a trench, viewed between strands of barbed wire. The men have only dug to about knee level and are very exposed, so it seems probable that they were not within sight of enemy trenches. Nearer the front line, trench digging was done under cover of night.
Barbed wire was used by both sides as a deterrent to slow an enemy attack as it approached the front of the trenches. It had been invented in 1873 in America as cattle fencing, but its nickname there seems even more apt to its use in warfare. It was called ‘The Devil’s Rope’.