My Father's House by Joseph O'Connor

September 1943: German forces have Rome under their control. SS Commander Paul Hauptmann rules over the Eternal City with vicious efficiency. The war’s outcome is far from certain. Diplomats, refugees, Jews, and escaped Allied prisoners flee for protection into Vatican City, a neutral, independent state nestled in the city of Rome. A small band of unlikely friends led by a courageous Irish priest is drawn into a deadly battle of wits with Hauptmann and his soldiers.