In chapter twenty-two why does the author include the story of Ted Lavender?

 Ted Lavender's death forces the men to face death, knowing that their lives could be taken away at any moment. They are all so happy when one soldier makes it through the tunnel, but then that small bit of happiness is taken away when Ted is shot while coming back from the bathroom. After his death, the men attempt to make sense of Ted's death in their own way. One doesn't want to talk about it, while Kiowa needs to talk. Each day, the men must face the possibility of their own deaths, but Ted's death seems so senseless. Lt. Cross burns all of  his personal effects having to do with Martha because he thinks that allowing himself to dream will get another man killed. Lt. Cross feels responsible for Ted's death and feels responsible for keeping the other men alive. As the platoon leader, Cross is "determined to perform his duties firmly and without negligence" because he thinks this is the only way he can keep himself and his men alive.