The Vatican's diplomatic efforts are based on its mission to promote universal values, human dignity, and neutrality in global matters. These issues emerged in the first half of the last century, and the Church's approach during this period was shaped by its theological foundations and historical context. The bulk of the thesis is dedicated to investigating the Vatican's relationships with key countries involved in World War II, such as Italy, Germany, and the Allies. This includes the controversial role of Pope Pius XII, particularly concerning accusations of passivity and alleged cooperation with fascist regimes. The analysis also addresses the complex interactions between the Vatican and Nazi Germany, including the Concordat signed with the Third Reich and the delicate balance the Vatican sought to maintain in its diplomatic relations. A specific chapter focuses on anti-Semitism and the Church's efforts to protect Jews, including hiding them within the Vatican, as well as the broader implications of these actions. The thesis also discusses the broader context of Vatican diplomacy, including humanitarian initiatives, attempts at peace negotiations, and the challenges the Vatican faced in maintaining neutrality while advocating for moral and ethical values. The conclusion reflects on the consequences of Vatican diplomacy during this period, taking into account both the criticisms and the defense of Vatican actions, with the overall aim of providing a comprehensive understanding of the Vatican's role in one of the most tumultuous periods in modern history.