“How to Tell a True War Story” is a section from Tim O’Brien’s The Things They Carried.
It begins with the narrator’s recounting the story of a buddy from in Vietnam named Rat Kiley who wrote a letter to the sister of Rat’s best friend in the war who had just been killed in action. Despite pouring his heart and soul into the letter, he never receives a reply. This introduces both the central character, Rat Kiley, in this section and the idea that “true” war stories are often anticlimactic.
In order to narrow down O’Brien’s thesis, as your question asks, one can examine the beginning and end to see what that is.
In the second paragraph, O’Brien states:
A true war story is never moral. It does not instruct, nor encourage virtue, nor suggest models of proper human behavior, nor restrain men from doing the things they have always done. If a story seems moral, do not believe it. If at the end of a war story you feel uplifted, or if you feel that some small bit of rectitude has been salvaged from the larger waste, then you have been made the victim of a very old and terrible lie.
This excerpt is thought provoking because it asserts that in order for a war story to be true, it can never have a happy ending. In addition, a true war story isn’t concerned will people behaving nobly and courageously in the face of mortal danger. In fact, O’Brien provides several examples in this story that portray the opposite of courage, such as Rat Kiley’s slow killing of the baby water buffalo.
O’Brien expands on his thesis near the end of the excerpt saying that,
a true war story does not depend upon that kind of truth. Happeningness is irrelevant. A thing may happen and be a total lie; another thing may not happen and be truer than the truth.
O’Brien suggests in this quote that a true war story isn’t actually concerned with the truth at all. He redefined what truth actually is, suggesting that a single snapshot of war is never adequate in describing the truth of the experience of war.
If one combines these two elements of a true war story, then O’Brien’s thesis becomes clear. There is no such thing as a true war story as long as one clings to the belief that it must have actually happened exactly as it is told.