As Robert rides ahead of Poole and the rest of the convoy, he accidentally puts his foot down in a sinkhole and falls in the mud up to his waist. Terrified of drowning, he desperately thrashes and claws his way out. Through the fog, Robert spots another soldier lying nearby before he is blinded by the mud’s natural chlorine.
Like the constant threat of gas, the random threat of sinkholes suggests that all external forces are potentially violent in war. Even when the enemy is far away, as Poole assured Levitt in Chapter 3, there is no opportunity for the soldiers to let their guard down or rest.
Eventually, Poole and Levitt catch up to Robert and help him up. Once his eyes have cleared, Robert looks back and realizes that the entire field is full of dead bodies floating in the mud, and that the sounds he and Poole had heard earlier were crows feeding on the corpses.
Robert’s realization that the body he saw is only one of many reflects the immense magnitude of World War I. While tragedies like the man lying in the mud initially feel personal and immediate, the sheer scale of the war means that Robert and the other soldiers will have to desensitize themselves to violence in order to stay sane.