The important theme of this brilliant short story is the way that war is shown to impact the soldiers that are part of it and involved in it. If we compare O'Brien's attitude in "Ghost Soldiers" to the idealism and desire to do the right thing that he displays in earlier stories, we can see that O'Brien has been greatly altered by his exposure to the ambiguity and horrors of war. In his insatiable desire for revenge against Jorgenson, we see no sense of obligation or responsibility. O'Brien uncovers a kind of central truth about himself as he experiences intense anger and the desire for revenge. Even though he is an intelligent and empathetic young man, he realises that war has transformed him to such an extent that he need to hurt others so he is able to avenge hurts that have been done to him. Consider the following quote:
I’d come to this war a quiet, thoughtful sort of person, a college grad, Phi Beta Kappa and summa cum laude, all the credentials, but after seven months in the bush I realized that those high, civilized trappings had somehow been crushed under the weight of the simple daily realities. I’d turned mean inside.
O'Brien is forced to concede that he is very capable of committing evil acts. O'Brien is now only able to cope with being hurt by returning that hurt. Note the way that this quote juxtaposes his former life of intellectual achievement and rationalism with the reality of his life in Vietnam, where titles and awards such as academic achievments have no relevance, and contrast massively with the "meanness" that O'Brien discovers inside of himself. This story clearly shows that the real victims of war are the soldiers that fight in that war.