This is an image of several fallen soldiers, half-buried in the trenches. Trench warfare became widely used during World War I, with some trenches being dug several hundered miles long! Althoough trenches provided an efficient way of to avoid the larger number of casualties that came with open warfare, there was nothing glamorous about life in the trenches. Living conditions were absolutely horrid, and unsanitary. In the first stanza of "Dulce Et Decorum Est", Wilfred Owen gives us a glimpse into trench life, by using negative connotations such as, "hags", "sludge", "haunting", (Lines 2-3). And with corpses such as the ones in the photograph above, they were usually buried where they fell, eventually attracting rodents and making conditions even more unsanitary.
Sources:
https://commons.m.wikimedia.org/wiki/File:FrenchTrenchWWI--nsillustratedwar03londuoft.jpeg
https://www.poetryfoundation.org/poems/46560/dulce-et-decorum-est