Eugenio Pacelli, Pope Pius XII, is one of the most studied but least understood popes of the twentieth century while his pontificate remains the most turbulent and controversial. Although there is a general consensus that he faced serious problems during his tenure -- fascist aggression, the Second World War, the Nazi genocide of the Jews, the march of communism, and the Cold War -- there is disagreement on his response to these developments. Applauded by some as an apostle for peace for his attempt to prevent the outbreak of war, he has been denounced by others as an advocate of appeasement...