The Things They Carried is a Vietnam War book by Tim O'Brien, based on his own experiences as a soldier. Lieutenant Jimmy Cross is the main character of the title story.
Cross is a young soldier, drafted like many others, and committed to the war effort and getting his men out alive. He is not emotionally or patriotically committed, instead simply seeing the war as his assigned job to which he gives his best effort. Initially, before the death of Ted Lavender, Cross is distracted from the day-to-day war by his feelings for a girl back home, Martha; her letters and photos are a fantasy for him:
He remembered kissing her good night at the dorm door. Right then, he thought, he should've done something brave. He should've carried her up the stairs to her room and tied her to the bed and touched that left knee all night long. He should've risked it. Whenever he looked at the photographs, he thought of new things he should've done.
In his head, Martha is a beacon of regret, symbolizing all the things he feels he should have done while he had the chance; Cross knows he might not get the chance later. As the war drags on and Cross loses his innocence, he gives the fantasy up:
He was realistic about it. There was that new hardness in his stomach. He loved her but he hated her.
No more fantasies, he told himself.
Henceforth, when he thought about Martha, it would be only to think that she belonged elsewhere. He would shut down the daydreams. This was not Mount Sebastian, it was another world, where there were no pretty poems or midterm exams, a place where men died because of carelessness and gross stupidity.
By divesting himself of the fantasy world, Cross becomes a better leader of his men; this is his only goal now in the war, since he feels that his men do not deserve to die but he cannot take their place.
Jimmy Cross did not want the responsibility of leading these men. He had never wanted it. In his sophomore year at Mount Sebastian College he had signed up for the Reserve Officer Training Corps without much thought... He was unprepared. Twenty-four years old and his heart wasn't in it. Military matters meant nothing to him. He did not care one way or the other about the war, and he had no desire to command....
(All Quotes: O'Brien, The Things They Carried, Google Books)
Cross feels responsible for their lives, but not for his own; he is committed to the war only in that it is a job. His guilt allows him to shoot his own foot, taking him out of the war, and when he returns home, it is hard for him to relate to others because of the mental damage from the war. Today, Cross would be seen as a typical victim of Post Traumatic Stress Disorder, and a standard "type" of Vietnam soldier: the drafted young man who is forever changed and damaged by the war.