I think it just depends on the kid, but I would absolutely be addressing the Japanese are tricky part, and get him a book on interment camps in the U.S. I would honestly be more concerned with the way the history was presented than with the graphic description. I don't think it is a negative thing for kids to learn about the real effects of war on individuals. And while I was older, maybe 9, when I read The Diary of Anne Frank I still remember being furious when my mom told me she thought I was too young to read it and that it was just depressing. I hid behind the couch to read it and silently fumed. I think giving him some additional context is appropriate.
http://www.amazon.com/Farewell-Manz...sr=1-5&keywords=japanese+interment+camps
