He was in Vienna on November 7, 1938, the same day a Polish teenager named Herschel Grynszpan assassinated a German diplomat, Ernst vom Rath, in Paris. The killing was used by the Nazis as the pretext for Kristallnacht, or the Night of Broken Glass, a pogrom against Jews. In Austria, Walker saw bonfires of Jewish books and the looting of Jewish businesses. Having written with alarm at the persecution of Christians, he expressed contempt for Catholic leaders showing deference to the Nazis, including Austrian Cardinal Theodor Innitzer, who met Hitler in 1939. Innitzer later withdrew support for the Nazi regime....