 It deals with the moral decisions made by people in the most testing of times and offers a perspective on human actions during wartime.Vollmann makes use of many historical figures as characters such as revolutionary Nadezhda Krupskaya, composer Dmitri Shostakovich, artist Käthe Kollwitz, film director Roman Karmen, poet Anna Akhmatova, SS officer Kurt Gerstein, activists Rosa Luxemburg and Karl Liebknecht, as well as German general Friedrich Paulus and Soviet general Andrey Vlasov.In an afterword, Vollmann admits that, while the book is heavily researched and mostly features real people, the work should be regarded as fiction.