The History of the Popes (Vol. II): From the Close of the Middle Ages focuses on the reigns of Popes Nicholas V, Calixtus III, and Pius II. The period 1447–1464 highlights major challenges such as the political upheavals of Italy, the fall of Constantinople, and the rise of art and literature. The book is divided into two major sub-chapters: Part 1: The Pontificate of Nicholas V (1447–1455) and Part 2: Popes Calixtus III & Pius II (1455–1464). Part I covers the election of Pope Nicholas V, initiating efforts at church unification and political reconciliation; the Jubilee of 1450 and the Restoration, focusing on the celebration of the Holy Year of 1450 and Nicholas V's appointment as patron of the Renaissance, where he sponsored a renewal of art, manuscripts, and architecture in Rome; and the revolt (threat) sparked by the Conspiracy of Stefano Porcaro in 1453 and the fall of Constantinople to the Ottoman Empire, which triggered a major crisis for Christendom. Part II covers the Crusades and Conquests; the election of Pope Calixtus III, which prioritized the Crusades, including the Christian victory at Belgrade and the activities of the Albanian hero Skanderbeg and the Congress of Mantua; the reign of Pope Pius II, focusing on the continuing threat of the Ottoman Empire and diplomacy at the Congress of Mantua; the settlement of the throne of Naples; and the preparation for Pius II's death in his efforts to organize the Crusades. This comprehensive work encompasses 40 volumes covering 56 popes.