The essays in this book cover a fast-paced 150 years of Vatican diplomacy, starting from the fall of the Papal States in 1870 to the present day. They trace the transformation of the Vatican from a state like any other to an entity uniquely providing spiritual and moral sustenance in world affairs. In particular, the book details the Holy See's use of neutrality as a tool and the principal statecraft in its diplomatic portmanteau. This concept of "permanent neutrality," as codified in the Lateran Treaties of 1929, is a central concept adding to the Vatican's uniqueness and, as a result, the analysis of its policies does not easily fit within standard international relations or foreign policy scholarship. These essays consider in detail the Vatican's history with "permanent neutrality" and its application in diplomacy toward delicate situations as, for instance, vis a vis Fascist Italy, Nazi Germany, and Imperial Japan, but also in the international relations of the Cold War in debates about nuclear non-proliferation, or outreach toward the third world, including Cuba and Venezuela. The book also considers the ineluctable tension between pastoral teachings and realpolitik, as the church faces a reckoning with its history.