In the linked series of fictionalized stories about his experiences during the Vietnam War The Things They Carried, author Tim O'Brien tells of Jim Cross's infatuation with Martha in the first chapter, also called "The Things They Carried." Cross's most treasured possessions are letters from Martha and photographs of her, which he keeps wrapped in plastic in his rucksack. O'Brien emphasizes that "they were not love letters," but Cross gets them out often to hold and read. As the platoon marches through the jungle, Cross remembers a movie date that he went on with Martha and imagines romantic excursions that he and Martha can take together.

Cross blames his distractedness in fantasizing about Martha all the time for the death of Ted Lavender, who is abruptly shot one day. At the end of that day, Cross digs a hole, goes inside, and mourns. O'Brien writes:

He felt shame. He hated himself. He had loved Martha more than his men, and as a consequence Lavender was now dead, and this was something he would have to carry like a stone in his stomach for the rest of the war.

The next morning Cross burns all of Martha's letters and photos even though he realizes that he "couldn't burn the blame." His attitude towards Martha changes. Instead of imagining a relationship with her, he decides that he hates her. Whenever the daydreams occur, he pushes them out of his mind.

O'Brien makes it clear that Cross realizes that Martha does not love him and that they don't have a real relationship. However, to Cross, Martha represents the ideal sort of life he would be having at home if he had not had to go to war. He uses the daydreams of Martha as a protective device to shield himself from the horrifying realities around him. When he thinks about her, he doesn't have to dwell on the blood, mangled bodies, and death that he encounters on a daily basis. He finally realizes, though, that he cannot continue the fantasy when his negligence gets Lavender killed.

Martha seems to represent home and normalcy, and she serves as a form of escape for Jimmy Cross as he struggles through the pressures and horrors associated with the Vietnam War. In "The Things They Carried," the narrator describes how Jimmy obsesses over Martha's letters and fantasizes about her and their relationship. Ironically, they really didn't have a romantic relationship; so much of what he imagines about her is pure invention. Martha becomes sort of an idea to Jimmy: she represents the pleasures of normal life, the comforts of home and the known back in the U.S., and the possibility of something beyond the war setting.

Eventually, in the title story, Ted Lavender is killed, and Jimmy Cross blames himself because he thinks Martha has distracted him. He decides to burn the letters and other items associated with Martha to purge himself of her influence. Jimmy vows to become harsher as a lieutenant and less friendly with his men; he sees this as taking his responsibility as their leader more seriously. On the other hand, one could argue that his choice to burn Martha's letters dehumanizes Jimmy to some extent and robs him of a necessary escape from the reality of war. Either way, Jimmy's "relationship" with Martha is complex and multi-faceted and conveys multiple associations in Tim O'Brien's story collection.

Perhaps because Jimmy Cross understands and fears that he could be killed at any time while on patrol, his thoughts turn toward unfulfilled dreams and desires. As the story unfolds, it becomes clear that Jimmy has read more into his relationship with Martha than what is truly there. In order for people in general, not just Jimmy, to be able to cope in life, they have to have a goal in front of them. If Jimmy can keep Martha in his mind, dreaming of her, and projecting himself into a future where she exists, he has a reason to keep moving forward. However, after Ted Lavender's death, Jimmy believes that he must rid himself of thoughts of Martha. He replaces thoughts of her with an intense focus on keeping his platoon alive.

To Lieutenant Jimmy Cross, who is fighting an atrocious war in Vietnam, Martha represents the safety and security of life at home. He carries letters from her about with him in the war. They aren't love letters, but he hopes that they are. He imagines trips with her to camp in New Hampshire, and his imagination takes flights of fancy about the life he could have with her. She is, Cross believes, a virgin. She is also an apt English student, and her letters are filled with admiration for Chaucer and Woolf. It is clear that Cross idolizes Martha as a pure and lovely individual who is far from the horror and hate that he sees every day in Vietnam. She is a symbol of everything that he imagines to be pure and good, but it is clear that he doesn't know her very well as a person. Instead, he treats her almost as if she were the Virgin Mary—an untouchable, pure figure whom he worships from afar.

I would argue that Martha actually represents lots of things to Cross, and she acts as quite a complex symbol in this short story. Most of all, however, she clearly represents escapism. Cross is shown as a man who is under a lot of pressure and so having Martha's letters allows him to dream and to escape the responsibilities and role that he has been given and that oppress him so greatly. Note how this is presented in the following quote:

He would imagine romantic camping trips into the White Mountains in New Hampshire. He would sometimes taste the envelope flaps, knowing her tongue had been there.

Clearly Cross needs this escapism and the way that he invests so much time and mental energy into "pretending" and creating lavish fantasies of love between himself and Martha indicates how important escapism is for him. Of course, this is something that he comes to view as a dereliction of his duty, as he comes to believe that this daydreaming was responsible for the death of one of his men.