My grandfather, Friedrich Jürgen Carl Brömel Berendsen (1904–1974) , generally known as Fritz Berendsen, lived through some of the most consequential transformations in German history. Born during the German Empire, he grew up through the First World War, became a cavalry officer in the Weimar Republic, served as a senior General Staff officer in the Wehrmacht, worked with the American military after the war, entered German industry and politics, and eventually became a major general in the Bundeswehr. His professional life was unusual not simply because of the positions he held, but because he moved repeatedly between institutions that belonged to very different political and constitutional systems. He served in the German army before and during the Nazi dictatorship, subsequently contributed to post-war economic and political life, and then returned to military service within the democratic Federal Republic and the NATO alliance. His experiences raise difficult questions about...