What does O'Brien compare and contrast war with in this chapter? What do we learn about the war?

The war was like a Ping-Pong ball, O’Brien writes: “You can put a fancy spin on it.” He is a 43-year-old writer. He can’t remember some things about the war. But the bad memories, like Kiowa sinking into a field or Curt Lemon being blown to pieces, keep playing over and over. O’Brien feels guilty about remembering these things and only writing war stories. His young daughter, Kathleen, tells him he should find a new topic and learn how to write a happy story. But O’Brien thinks that this task is almost impossible.