In the novel, Lt. Jimmy Cross is an officer in charge of Alpha Company during the Vietnam War. He embodies all the characteristics of a soldier torn between duty and self-preservation. Having originally signed up for ROTC (Reserve Officer Training Corps) while in college, he is ashamed that the only reason he signs up is because some of his friends are also signed up. He goes into war with a double mind, and as a result, he constantly finds himself fantasizing about his girlfriend, Martha, while leading his men through the jungle. Although Martha writes to him, we readers are aware of the dramatic irony of this relationship: she doesn't really love him and is just going through the motions of love.
"Lieutenant Cross understood that Love was only a way of signing and did not mean what he sometimes pretended it meant."
When one of his men, Ted Lavender, is killed, Lt. Jimmy Cross blames his inattentiveness for Lavender's death. Years later, he confesses to Tim O'Brien that he has never forgotten nor forgiven himself for that death. When Lavender died, he was carrying
"...more than 20 pounds of ammunition, plus the flak jacket and helmet and rations and water and toilet paper and tranquilizers and all the rest, plus the unweighed fear."
Lt. Cross eventually burns all Martha's letters as self-punishment for the death of Lavender. He believes that "Ted Lavender was dead because he loved her so much and could not stop thinking about her." Yet he is helpless in the face of his grief and guilt; he falls back into his fantasy world in order to cope with Lavender's death, the atrocities of war and its mind-numbing degradation.
"...he would slip away into daydreams, just pretending, walking barefoot along the Jersey shore,with Martha, carrying nothing. He would feel himself rising. Sun and waves and gentle winds, all love and lightness."
Despite this coping mechanism, Cross would always blame himself for Lavender's death.
"When a man died, there had to be blame. Jimmy Cross understood this. You could blame the war. You could blame the idiots who made the war...In the field, though, the causes were immediate. A moment of carelessness or bad judgment or plain stupidity carried consequences that lasted forever."