| Quote #1
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 Things They Carried.42)
It's hard to say whether or not we're supposed to think Jimmy Cross is being unreasonable here. On the one hand, it's our automatic response to reassure him and say that just loving Martha couldn't possibly have caused Lavender's death. On the other hand, this is war, and he's the commanding officer. It's very possible that his distraction over Martha caused Lavender to die.
| Quote #2
In any other circumstances it might've ended there. But this was Vietnam, where guys carried guns, and Dave Jensen started to worry. (Enemies.2)
We see a situation here that has guilt and blame over a couple of simple things – a stolen jackknife, a broken nose. Simple enough. But, in Vietnam, those kinds of things fester. The presence of guns and the overall tension amplify the guilt and blame and make them so much worse.
| Quote #3
Later we heard that Strunk died somewhere over Chu Lai, which seemed to relieve Dave Jensen of an enormous weight. (Friends.13)
Dave Jensen feels guilty for not killing Lee Strunk and putting him out of his misery. It seems as if the soldiers are in a damned-if-you-do, damned-if-you-don't situation: Jensen would probably have felt guilty if he'd killed Strunk as per their original pact, but not killing his friend made him feel guilty, too.