World War I influenced J.R.R. Tolkien’s depiction of the Dead Marshes. Tolkien served in the British Army during the First World War and experienced the Battle of the Somme in 1916.
The Dead Marshes, crossed by Frodo and Sam near Mordor, contain pools in which faces of fallen warriors appear beneath the water. Tolkien later explained that his wartime experiences contributed to the imagery, although the scene is not a direct historical allegory of one battlefield.
Tolkien strongly resisted simple one-to-one interpretations of his fiction. His wartime service nevertheless provided firsthand knowledge of trenches, devastated landscapes, fear, exhaustion, and the loss of comrades. The Dead Marshes are therefore best understood as a fictional landscape shaped partly by memories of World War I rather than as a literal retelling of the Somme.