When the jolly Italian peasant-turned-cardinal Angelo Giuseppe Roncalli of Venice was elected Pope John XXIII in 1958, change was in the air. The Church, many said, had refused to enter the twentieth century. In response, Pope John launched Vatican II, an “ecumenical council” that summoned hundreds of church leaders to Rome. It marked one of the most progressive turns the Church had taken in centuries: “medicine of mercy,” as Pope John called it. Yet not everyone in the Church was prepared to accept this modernization. The lines were drawn—in a battle that continues to rage into the twenty-first century.