Lt. Cross functions as a metaphor for the war, specifically its lack of meaningful structure. Like the war, Lt. Cross is characterized by a lack of definite purpose. Lt. Cross's role as leader of Alpha Company should be that of a strong leader who gives his troops clear instructions for gaining measurable advantage over the enemy. The nature of the Vietnam War, however, makes this kind of leadership impossible because the steps to achieve the objective of the war are undefined and obfuscated. Similar to battles and operations that constituted the war, Cross fails to demonstrate the clear ability to fulfill his role.
Lt. Cross is a weak leader because the traditional training he received is at stark odds with what he encounters in-country. His training forced him to be concerned more with marching in line, following preset maps, and keeping guns clean — following pre-decided standard operating procedures — rather than adapting to his environment and the attitude of his men. He was the leader of Alpha Company but never a true member of it, separating himself from his men in order to maintain a position of authority that he could never maintain if not for his superior rank. He never demonstrates leadership, but instead is granted it by decree. He lives for the knowledge that he is a leader, but is constantly afraid of that role. For example, Lt. Cross attempts to persuade himself of his own competence by relying on standard operating procedure after Lavender is killed as a means to exonerate himself from feelings of personal culpability in Lavender's death as well as his pathetic neediness for Martha's love.
Cross's other character defect is his personal and emotional inability to lead Alpha Company. He jealously guards a photograph of Martha, a girl who is not his girlfriend, to maintain a strong link to love and his life at home. He fails to recognize, however, how love and war are connected, relying instead on his love for Martha as an escape from war. He cannot be both in love and in war; just as his relationship with Martha is a fiction, so is his ability to perform his soldierly duties. By loving, therefore, he actively resists his duty as a leader — he withdraws from leadership and Vietnam.
Cross is a foil to "O'Brien" because Timmy and Linda share a true love story and Cross and Martha do not. Martha is the object of Cross's sexual desire, Linda is not the subject of O'Brien's; Martha prevents Cross from being a soldier, Linda teaches Timmy about death. O'Brien's story is a true love story; Cross's is a war story; the primary function Cross serves in the novel is to demonstrate how sometimes stories are not cathartic, but sources of denial.