The state was legally established in the 8th century when Pepin the Short, king of the Franks, gifted 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.

At their zenith, the Papal States covered most of the modern Italian regions of Lazio (which includes Rome), Marche, Umbria, Romagna, and portions of Emilia.

[11] Early congregations met in rooms set aside for the purpose in the homes of wealthy adherents, and a number of titular churches located on the outskirts of Rome were held as property by individuals, rather than by any corporate body.

As central Roman authority disintegrated throughout the late 5th century, control over the Italian peninsula repeatedly changed hands, falling under the Arian suzerainty of Odoacer in 473, and in 493, Theodoric, king of the Ostrogoths.

Justinian established the Exarchate of Ravenna of which the Duchy of Rome, an area roughly coterminous with modern day Lazio, was an administrative division.

By the 7th century, Byzantine authority was largely limited to a diagonal band running roughly from Ravenna, where the emperor's vicar, or exarch, was located, to Rome and south to Naples, plus coastal exclaves.

As Byzantine power weakened, though, the papacy assumed an ever-larger role in protecting Rome from the Lombards, but lacking direct control over sizable military assets, the pope relied mainly on diplomacy to achieve as much.

A climactic moment in the founding of the Papal States was the agreement over boundaries contained in the Lombardic King Liutprand's Donation of Sutri (728) to Pope Gregory II.

[22] When the Exarchate of Ravenna finally fell to the Lombards in 751,[23] the Duchy of Rome was completely cut off from the Byzantine Empire, of which it was theoretically still a part.

[24] In practice, the popes were unable to exercise effective sovereignty over the extensive and mountainous territories of the Papal States, and the region preserved its old system of government, with many small countships and marquisates, each centred upon a fortified rocca.

[25] Yet over the next two centuries, popes and emperors squabbled over a variety of issues, and the German rulers routinely treated the Papal States as part of their realms on those occasions when they projected power into Northern and Central Italy.

As the Gregorian Reform worked to free the administration of the church from imperial interference, the independence of the Papal States increased in importance.

In response to the struggle between the Guelphs and Ghibellines, the Treaty of Venice made official the independence of the Papal States from the Holy Roman Empire in 1177.

The resulting aristocratic anarchy in the city provided the setting for the fantastic dreams of universal democracy of Cola di Rienzo, who was acclaimed Tribune of the People in 1347,[35] and met a violent death in early October 1354 as he was assassinated by supporters of the Colonna family.

In 1527, before the Holy Roman Empire fought the Protestants, troops loyal to Emperor Charles V brutally sacked Rome and imprisoned Pope Clement VII, as a side effect of battles over the Papal States.

[40][39] A generation later the armies of King Philip II of Spain defeated those of Pope Paul IV in the Italian War of 1551–1559, fought to prevent growing Spanish dominance in Italy.

In 1512 the state of the church annexed Parma and Piacenza, which in 1545 became an independent duchy under an illegitimate son of Pope Paul III.

[44] In 1649, after the annexation of the Duchy of Castro, the Papal States reached their greatest extent, including most of central Italy – Latium, Umbria, Marche, and the legations of Ravenna, Ferrara, and Bologna extending north into the Romagna.

[45] Two years later, French forces invaded the remaining area of the Papal States, and in February 1798 General Louis-Alexandre Berthier declared a Roman Republic.

In June 1800, French Consulate formally concluded the occupation and restored the Papal States, with the newly elected Pope Pius VII taking residence in Rome.

Yet, in 1808 the French Empire under Napoleon invaded again, and this time on 17 May 1809 the remainder of the States of the Church were annexed to France,[45] forming the départements of Tibre and Trasimène.

Following the fall of the First French Empire in 1814, the Congress of Vienna formally restored the Italian territories of the Papal States, but not the Comtat Venaissin or Avignon, to Vatican control.

Italian nationalism had been stoked during the Napoleonic period but dashed by the settlement of the Congress of Vienna (1814–15), which sought to restore the pre-Napoleonic conditions: most of northern Italy was under the rule of junior branches of the Habsburgs and the Bourbons.

[47] As a result of the Second Italian War of Independence, Piedmont-Sardinia annexed Lombardy, while Giuseppe Garibaldi overthrew the Bourbon monarchy in the south.

King Victor Emmanuel II at first aimed at a peaceful conquest of the city and proposed sending troops into Rome, under the guise of offering protection to the pope.

Although the Pope's tiny army was incapable of defending the city, Pius IX ordered it to put up more than token resistance to emphasize that Italy was acquiring Rome by force and not consent.

This incidentally served the purposes of the Italian State and gave rise to the myth of the Breach of Porta Pia, in reality, a tame affair involving a cannonade at close range that demolished a 1600-year-old wall in poor repair.

However, throughout the history of the Papal States, many warlords and even bandit chieftains controlled cities and small duchies without having received any title from the Pope of the day.

[53] In 1861 an international Catholic volunteer corps, called Papal Zouaves after a kind of French colonial native Algerian infantry, and imitating their uniform type, was created.

Predominantly made up of Dutch, French and Belgian volunteers, this corps saw service against Garibaldi's Redshirts, Italian patriots, and finally the forces of the newly united Italy.