The first archetype that jumped out at me as soon as I started reading the story was the novel design of letter writing. There are many stories of soldiers writing letter to their sweathearts at home. Now there are even modern parallels to that archetype; writing e-mails in long distance relationships, texting. Now, even more than then, letters across a long distance are romantic and personal. In Vietnam, or in previous wars, there were no cell phones and no way to skype or video chat.
The soldier and the sweatheart waiting at home are two archetypes in themselves. There are many different variations of that relationship that can play out in a story. The soldier dying and the girl finding out is another. The man returning home changed is another.
The soldier in the jungle is another archetype. It's uncharted territory, almost like the forest in "Young Goodman Brown." At night, the jungle is even more complicated by the fact that it is even more dangerous in the dark.
I was really interested by the passage about superstition. The soldiers are very superstitious, it can't really hurt to try to attract good luck. This is a section, I believe may challenge cultural norms about superstitions. The soldiers carry good luck charms but they seem to be charms determined by their setting. A normal good luck charm may be a religious symbol, and a rabbit's foot that one soldier does have, but another carries a pebble and another, a thumb. The thumb definitely challenges the normal good luck charm. Although it is mentioned in the story that there is a moral associated with the thumb, "Have gun, will travel," The other soldiers don't really seem to understand why that is associated with the thumb. I, a reader, didn't really get it either. When considering that it is the thumb of an enemy and a young boy not too much younger than they are, the thumb does make sense, but I would not expect a person away from the war to be carrying a thumb around for good luck. The thumb would be a great topic of discussion for the classroom.