The Secretariat for Promoting Christian Unity, tasked with addressing relations with Jews in the preparations for Vatican II, eventually assumed responsibility for three groundbreaking texts on ecumenical relations, interreligious relations, and religious liberty. The sixteen documents and other conciliar acts of Vatican II build on one another and unfold thematically. One needs to study the whole of Vatican II to understand these developments, as Paul VI observed at its close. The1964 encyclical of Paul VI on the church, Ecclesiam Suam, provided a basis for a theology of communion while the 1963 encyclical, Pacem in Terris, of John XXIII on world peace provided a basis for an expansion of Catholic social teaching into the modern world of global politics and religious diversity. Following the council, interreligious dialogue and relations, as promoted by the Catholic Church but developed in various kinds of interreligious projects and events, has followed two paths, one largely of spiritual engagement and edification and mostly through social and political and social engagement. Despite the claim that Nostra Aetate had a "purely religious character," the document carried political implications for 1965, and the interreligious relations that it launched for Catholics unfolded in diverse and interrelated religious and political contexts. Major milestone for understanding the value of interreligious dialogue were both political and religious. These will be noted. The character of interreligious relations has consequently changed with successes and failures. That will be discussed as well. The 2020 encyclical of Pope Francis, Fratelli Tutti, on fraternity and social friendship, although the pope himself identified it as "a social encyclical," is the long-awaited encyclical on interreligious dialogue, framed with his particular understanding of dialogue as accompaniment and encounter.