The History of the Popes (Vol. XXI) : From the Close of the Middle Ages examines the pontificate of Pope Sixtus V (1585–1590). The book explores the actions of this brilliant yet controversial Franciscan pope a reformer and statesman who successfully overhauled papal administration and radically transformed the face of Rome during his brief tenure. Additionally, the author details Sixtus V’s efforts to eradicate corruption and crime within the Papal States. He undertook a massive reorganization of the Roman Curia and restored Vatican finances, transforming the Holy See into one of the most powerful economic forces in Europe at the time. The book also covers the Pope's ambitious urban development projects; under his rule, Rome was revitalized through the construction of new roads and aqueducts, the erection of the obelisk in St. Peter's Square, and the completion of the dome of St. Peter's Basilica. Further analysis focuses on the Vatican's role on the global political stage, including strained relations with Spain, France, and England specifically the events surrounding the Spanish Armada in the late 16th century. The book strikes a balance between praising the efficiency of his papacy and criticizing his sometimes authoritarian style of governance. This comprehensive work spans a total of 40 volumes chronicling the history of 56 popes.