In April 1963 an elderly and gravely ill Pope John XXIII addressed the countries and lands that had been a heartbeat away from atomic war in the Cuban missile crisis. It was his last encyclical, Pacem in terris, the first of its kind to speak not only to Catholics but to "all Men of Good Will". We are already familiar with the text and impact of this document, which was one of Pope Roncalli's most important contributions to his council. But in this book Alberto Melloni brings to light for the first time the discussions surrounding its writing and the various proposals by those who advised the Pope, who in the encyclical would take an unprecedented stance on the dignity of conscience, the distinction between movements and ideologies, and the mentality of the 'just war'. In a world that had witnessed the fall of the Berlin wall, but had not yet experienced the tensions that would lead to Kennedy's assassination and the demise of Khrushchev, Pacem in terris interpreted the future without moralizing, and succeeded in changing the perceptions of the church and the world at large.