"The Sweetheart of the Song Tra Bong" is not my favorite story, but it is one of the most popular stories in the novel and it has important and teachable themes. My objection to the story lies in its plausibility. A civilian girlfriend of a GI was not going to visit her boyfriend in an area of action in Vietnam. The plot seems juvenile to me, a fantasy of the mind of someone who wanted it to happen. Tim O'Brien distances himself from the story somewhat by making the narrator have the story come from the character of Rat Kiley, but he does not succeed.
A motif found by one of my classes in 2001 depends on the oral tasting and swallowing metaphor. Mary Anne wears her necklace of tongues. Rat Kiley describes her as a person who has "tasted" the war as other civilians back home have not. Mary Anne says, "Sometimes I want to eat this place. Vietnam. I want to swallow the whole country -- the dirt, the death -- I just want to eat it and have it there inside me." For Mary Anne, coming to Vietnam irrevocably changed her. She found something in life she wanted to consume and in the end the country, the jungle, the war consumed her.
Please note: The "Greenies" of the story are Green Berets, special forces of the army. They are the army equivalent of Navy SEALS. They are elite troops who possess special combat and survival training. I have assumed in the past that everyone would have known this, but I have recently discovered that I am in error about this.