It is fantastic what a wide range of stories there are about World Wars 1 and 2 for children covering all sorts of issues that people may not be aware of. Conscientious Objectors, the war in Italy, and this story about the resistance to Nazi occupation in Denmark are all covered by books on this site.
Number The Stars is a wonderful story about Anne Marie Johansen from Copenhagen and her best friend Ellen, who is Jewish. As the German occupation of Denmark unfolds Anne Marie can't understand why Mrs Hirsch's Neighbourhood shop has been closed. As more and more Jewish families leave Anne Marie learns more about the war and about her family.
In a breathtaking finale she ends up becoming a war hero for herself.