O'Brien uses irony, symbol, and point of view to show the reader different angles of war and how he feels about it. By doing this he can jump around and explore angles of his feelings before the war, during the war, and after the war much better.
In the chapter The Man I Killed he talks about a man he killed and what he looked like after he died and how he feels about the man's death. Then in the next chapter he goes into exactly what happened and how others reacted towards him. In the man I killed he gets his readers really curious as to what happened and who he is talking about. In Ambush, the next chapter he acts as though he is telling the story to his daughter, and he fills the readers in.
The second chapter, Ambush, is the real story of what happened, but reading, The Man I Killed, right before that makes everything he experienced in Ambush so much more powerful than it would have been if, The Man I Killed, wasn't included in the book.
O'Brien's use of point of view, symbol, and irony allow him to tell many different powerful stories that happened to him, and people that he knew to help express his thoughts on war.