Temporal power of the Holy See in the context of "Pope Pius IX"

Vatican City, officially the Vatican City State (Italian: Stato della Città del Vaticano; Latin: Status Civitatis Vaticanae), often shortened as the Vatican, is a landlocked sovereign city-state. Ruled by the pope, it is an enclave within Rome and serves as the administrative centre of the Catholic Church. Vatican City is governed by the See of Rome, commonly known as the Holy See, itself a sovereign entity under international law, which maintains its temporal power, governance, diplomacy, and spiritual independence. Vatican is also used as a metonym for the Holy See, which is the central governing body of the Catholic Church and Vatican City, comprising the pope and the Roman Curia. The independent state of Vatican City came into existence in 1929 via the Lateran Treaty between the Holy See and the Kingdom of Italy, which spoke of it as a new creation, not as a vestige of the much larger Papal States (756–1870), which had previously encompassed much of Central Italy.

With an area of 48.99 hectares (121 acres) and a population of about 882 in 2024, it is the smallest sovereign state in the world both by area and by population. It is among the least populated capitals in the world. As governed by the Holy See, Vatican City State is an ecclesiastical or sacerdotal-monarchical state ruled by the pope, who is the bishop of Rome and head of the Catholic Church; the highest state functionaries are all Catholic clergy of various origins. The Holy See dates to early Christianity and is the principal episcopal see of the Catholic Church, which in 2018 had about 1.329 billion baptized Catholics in the world, in the Latin Church and 23 Eastern Catholic Churches. After the Avignon Papacy (1309–1377) the popes have mainly resided at the Apostolic Palace within what is now Vatican City, although at times residing instead in the Quirinal Palace in Rome or elsewhere.

The Papal States (/ˈpeɪpəl/ PAY-pəl; Italian: Stato Pontificio; Latin: Dicio Pontificia), officially the State of the Church, were a conglomeration of territories on the Italian peninsula under the direct sovereign rule of the pope from 756 to 1870. They were among the major states of Italy from the 8th century until the unification of Italy, which took place between 1859 and 1870, culminating in their demise.

The state was legally established in the 8th century when Pepin the Short, king of the Franks, gave Pope Stephen II, as a temporal sovereign, lands formerly held by Arian Christian Lombards, adding them to lands and other real estate formerly acquired and held by the bishops of Rome as landlords from the time of Constantine onward. This donation came about as part of a process whereby the popes began to turn away from the Byzantine emperors as their foremost temporal guardians for reasons such as increased imperial taxes, disagreement with respect to iconoclasm, and failure of the emperors, or their exarchs in Italy, to protect Rome and the rest of the peninsula from barbarian invasion and pillage.

Pope Boniface VIII (Latin: Bonifacius PP. VIII, Italian: Bonifacio VIII; born Benedetto Caetani; c. 1230 – 11 October 1303) was head of the Catholic Church and ruler of the Papal States from 24 December 1294 until his death in 1303. The Caetani family was of baronial origin with connections to the papacy. He succeeded Pope Celestine V, who had abdicated from the papal throne. Boniface spent his early pontificate abroad in diplomatic roles.

Boniface VIII put forward some of the strongest claims of any pope to temporal as well as spiritual power. He involved himself often with foreign affairs, including in France, Sicily, Italy, and the First War of Scottish Independence. These views, and his chronic intervention in temporal affairs, led to many bitter quarrels with Albert I of Germany, Philip IV of France, and Dante Alighieri, who expected the pope to soon arrive at the eighth circle of Hell in his Divine Comedy, among the simoniacs.

The capture of Rome (Italian: Presa di Roma) occurred on 20 September 1870, as forces of the Kingdom of Italy took control of the city and of the Papal States. After a plebiscite held on 2 October 1870, Rome was officially made capital of Italy on 3 February 1871, completing the unification of Italy (Risorgimento).

The capture of Rome by the Royal Italian Army brought an end to the Papal States, which had existed since the Donation of Pepin in 756, along with the temporal power of the Holy See, and led to the establishment of Rome as the capital of unified Italy. It is widely commemorated in Italy, especially in cathedral cities, by naming streets for the date: Via XX Settembre (spoken form: "Via Venti Settembre").

The Donation of Pepin, or Donation of Pippin, was the transfer of Frankish territory in central Italy to Pope Stephen II made by Pepin the Short, King of the Franks, in 756. Credited with "effectively establishing the temporal authority of the papacy," the Donation took place amid the Byzantine Empire's decline in Italy and marked both "an important moment in the papal–Carolingian alliance" and an "important step" in the formation of the Papal States. With the fall of the imperial capital in Italy, Ravenna, to Aistulf, King of the Lombards in 751, "any semblance of imperial protection for Rome" had evaporated and the pope, who had technically been a Byzantine subject to this point, turned to Pepin for assistance. Pepin invaded Italy and, following an initial victory in 755, he decisively "defeated Aistulf and imposed a peace on him" in 756.

Pepin had promised Italian lands to Stephen II at a meeting in Quierzy, France in April 754. While this earlier promise is "often identified as the Donation," it may have been only verbal and "does not exist in written form." Papal accounts of the 754 promise state that Pepin "granted the pope the exarchate, including Ravenna, and the Roman duchy." In 756, the "Confession of St. Peter," a document listing the cities involved in the Donation, was "placed on the altar of Old St. Peter’s Basilica in Rome" along with "keys of the cities and territories in central Italy." The Confession document was created "following Pippin’s second invasion of Italy to assist the pope." After his initial invasion in 755, Pepin concluded the First Peace of Pavia, but Aistulf "refused to abide by" this agreement and attacked Rome. Pepin then defeated Aistulf again, imposing "heavy penalties" with the Second Peace of Pavia in 756.