During the Second World War, as the Soviet Red Army was locked in brutal combat against the Nazis, Joseph Stalin ended the state's violent, decades-long persecution of religion. In a stunning reversal, priests, imams, rabbis, and other religious elites--many of them newly-released from the Gulag--were tasked with rallying Soviet citizens to a "Holy War" against Hitler. To the delight of some citizens, and to the horror of others, Stalin's reversal...