To tell a true war story by Tim O'Brien, you need to look for authenticity in the characters' experiences and their inner thoughts. He often uses personal perspectives to convey the truth of war.
I think it's about presenting the complexity and chaos of war without sugar-coating. O'Brien might incorporate multiple viewpoints and unexpected elements to make the story truly genuine.
One way could be through vivid and honest descriptions of events and emotions. O'Brien might focus on raw details to make it feel real.