To make it easier to narrow down our options, we might start with a definition of guilt. According to a New York Times article by Nancy Sherman, there are basically two types of guilt: subjective guilt and objective guilt/rational guilt. Subjective guilt is when we feel responsible for our perceived wrongdoing despite little evidence, or even evidence to the contrary. This guilt may be inspired by factors beyond our control (more on this later). Objective/rational guilt occurs when our wrong actions actually cause harm in some way.
Lt. Cross' guilt seems to be more of the subjective kind. In the story, Cross carries letters from Martha and photographs of the English major with his gear. When he isn't going through the motions of being the leader or engaging in tasks expected of one, Cross daydreams about romantic liaisons with Martha. Cross steps away from his elaborate make-believe world of 'sun and waves and gentle winds, all love and lightness' only long enough to perform the necessary functions of a leader. O'Brien states that Cross carries 'responsibility for the lives of his men' on his shoulders.
When Ted Lavender is shot while relieving himself, Cross feels responsible. After all, he was daydreaming about Martha when it happened. O'Brien's often choppy and disjointed descriptions of Cross' dysfunctional perceptions and illusions about Martha (while out on patrol) highlights the lieutenant's own feelings of inadequacy, fear, helplessness.
Here, we can formulate a reason for Cross' guilt: his feelings of helplessness and inadequacy renders him defenseless to stop the senseless slaughter of his men. The next step is to determine where these feelings of inadequacy comes from. We can go to history for some answers.
1) The lack of a clear mission plan to accomplish the objectives of the war, which is to prevent the communist takeover of South Vietnam. Factors include difficult and unknown terrain, an elusive enemy who engages in unpredictable tactics, and inadequate military training to navigate such challenges.
2) Tens of thousands of young American lives were lost during the war. The average age of the American soldier was nineteen during the Vietnam War.
At this point, we can begin to formulate a couple of thesis statements about guilt:
1) Subjective guilt often results from factors beyond our control.
2) Irrational guilt stems from the human need to define the purpose and meaning of suffering.
Cross' physical burdens parallels the psychological and emotional burdens he carries inwardly. As we have established, Cross feels responsible for Lavender's death. The conflict between the desire to help, frustrated by the inability to, is at the root of Cross' guilt. To give anything other than unconditional care and protection is anathema in the military; the martial creeds of fidelity and honor are powerful sources of comfort for the soldier.
Survivor's/subjective guilt, then, is a way to share in the fates of fallen comrades. This is empathic distress. It is an effort to hold on to sanity, to define the purpose of fighting, and an effort to suffer with those one could not help. I close with a quote from Elizabeth Kubler Ross:
Consciously or not, we are all on a quest for answers, trying to learn the lessons of life. We grapple with fear and guilt. We search for meaning, love, and power. We try to understand fear, loss, and time. We seek to discover who we are and how we can become truly happy.