How does Chapter 11 connect to Chapters 10 & 12?

Chapter Eleven takes the form of a flashback to a few months earlier, when Bruno's family still lived in Berlin. Chapter Ten ended with Bruno's question to Shmuel: "Why are there so many people on that side of the fence? And what are you all doing there?" Chapter Twelve then returns to Bruno and Shmuel's conversation from opposite sides of the fence. We are aware of Bruno's past, but in Chapter Twelve, Shmuel answers Bruno's questions by explaining his own experiences.