Germany Must Perish is a 1941 political screed written by Theodore Kaufman. You can find a modern reproduction at Ostara Publications. This book was seized upon by Propaganda Minister Goebbels as a perfect book for him to use in radio broadcasts to show Germans what the Allies had in store for them.
The book describes itself “a comprehensive plan for the extinction of the German nation and the total eradication from the earth, of all her people.” Whether or not the book influenced Roosevelt is unknown, but a similar view of Germans was held by him regardless. The author dehumanizes Germans as separate from “humanity,” as beings of “Darkness.” The German people are at fault for the war and must be made to pay for it.