Civil Wars (1st century BC)

The institutions of the Roman republic, born for governing a city-state, were unfit to rule over such a large empire. Furthermore, there was discontent both inside Rome and between Rome and its Italic allies, and the tension favored military commanders, who started taking dictatorial powers. The first of these was Sulla, who prevented an overthrow of the republic by Marius but became a sort of "lord protector" of the Senate until his death (78 BC). After him came Julius Caesar, who after conquering the Gaul (present day France) won a civil war against Pompey but was assassinated by senators fearing he would start a monarchy, in 44 BC.

He was avenged by his nephew Octavianus who first defeated the senatorial party with the help of Mark Antony, and later (31 BC) Antony himself (who was allied to the queen of Egypt, Cleopatra).

The Roman Empire (1st-2nd centuries AD)

Octavianus was awarded the titles of Augustus and Princeps by what remained of the Senate, and was proclaimed Imperator (which at the time only meant "supreme commander") by his Legions. Even if he was careful to abide the rules of the old republic, Octavianus actually ruled as an Emperor, and the Roman Empire was born. This became apparent in 14, when he died and was succeeded by his adoptive son Tiberius.

The establishment of the empire brought substantial benefits to the provinces, which could now appeal to the emperor against rapacious administrators, rather than to the corrupt senatorial class to whom the administrators usually belonged. Furthermore, Roman citizenship was slowly extended to the provinces, and the rule of law became less arbitrary (although largely imperfect).

Despite its military strength, the empire made few efforts to expand its already vast extent; the most notable was probably the conquest of England by emperor Claudius in 47. In the 1st and 2nd century Roman legions were mostly employed in brief civil wars (e.g. in 68, the year of the four emperors) or suppressing insurrections (e.g. the Hebraic insurrection in Judea, ended with the destruction of the Temple of Jerusalem in 70, and with the start of the diaspora).

Decline and Fall (3rd-5th centuries)

In fact, the internal situation was slowly deteriorating, and exploded in the crisis of the Third Century, when economic problems, barbarian incursions and civil wars led to an almost complete disintegration of the empire. It was saved by Diocletian (284-305) and Constantine (306-337), who split the empire into a Western and an Eastern part, with Rome and Constantinopolis (founded by Constantine himself) as capitals. Constantine also stopped opposing the diffusion of the Christian religion (313, Edict of Milan), actually allying with the Christian church. Christianity became the only official religion of the empire in 380 under emperor Theodosius.

Italy in the Middle Ages

Goths, Byzantines, Lombards (6th-8th centuries)

Italy was invaded by the Visigoths in the 5th century, and Rome was sacked by Alaric in 410. By the end of the century the peninsula was mostly under Ostrogothic control, and the last Western Roman emperor, Romulus Augustus, was deposed in 476 by Odoacer. On February 25, 493 Theodoric the Great defeated Odoacer and became the king of the Ostrogoths and moved the capital to Ravenna.

The eastern half of the Empire, now centred on Constantinople, invaded Italy in the early 6th century, and the generals of emperor Justinian, Belisarius and Narses, conquered the Ostrogothic kingdom after years of warfare, ending in 552.

The collapse of the Ostrogoths allowed the Lombards to fill the gap, and the Eastern Empire could not hold on to its reconquered territory against the Lombard invasion. The Lombards ruled Italy until the late 8th century when in 774 their kingdom was conquered by Charlemagne.

Rise of the Catholic Church (4th century-8th century)

The Church (and especially the bishop of Rome, the pope) had played an important political role since the times of Constantine, who tried to include it in the imperial administration.

In the politically unstable situation after the fall of the western empire, the Church often became the only stable institution and the only source of learning. Even the barbarians had to rely on clerics in order to administrate their conquests. Furthermore, the catholic monastic orders, such as the Benedictines had a major role both in the economic life of the time, and in the preservation of the classical culture.

After the Lombard invasion, the popes (i.e. St. Gregory) were nominally subject to the eastern emperor, but often received little help from Constantinople, and had to fill the lack of stately power, protecting Rome from Lombard incursions; in this way, the popes started building an independent state.

The Holy Roman Empire (9th-10th centuries)

At the end of the 8th century the popes definitely aspired to independence, and found a way to achieve it by allying with the Carolingian dynasty of the Franks: the Carolingians needed someone who could give legitimacy to a coup against the powerless Merovingian kings, while the popes needed military protection against the Lombards. As a result, in 774 the Franks invaded the Kingdom of Italy and defeated the Lombards, and their leader Charlemagne was proclaimed legitimate king of the Franks by the pope (rex francorum et langobardorum). Later, on December 25, 800, Charlemagne was also crowned emperor of the Holy Roman Empire by the pope, triggering controversy and disputes over the Roman name. The new emperor (who was never recognized as such by the Byzantines) immediately conceded direct rule over central Italy to the pope, creating the Papal States.

The Imperial authority never extended much southwards the Italian peninsula. Southern Italy was divided amongst the two Lombards duchies of Spoleto and Benevento, who accepted Charlemagne's suzerainty only formally (812), and the Byzantine Empire. Coastal cities like Gaeta, Amalfi, Naples on the Tyrrhenian Sea, and Venice on the Adriatic, were Latin-Greek enclaves who were becoming increasingly independent from Byzantium. A conquest of Benevento, otherwise, would have meant the total encompassment of the Papal territories, and probably Charlemagne thought it was good for his relationships with the Pope to avoid such a move. The King's stron hold over his empire, on the other side, thwarted the ambitious program of Popes like Hadrian I, whose looser interpretation of the Peppin's donation (confirmed by Charlemagne in 774) extended ideally Papal authority over far territories including even Histria and Corsica. Such a vision would imply an almost total independence of the Pope, and Charlemagne was able enough to choke it. The Pope, by himself, had no other choice but submit. His local forces were feeble, or even rebellious: all the incoronation events were spurred by an attempt by a Rome's party to kill the Pope. The Lombard dukes were over, or untrustful. The Byzantines had little to give, and Charles had sharply left untouched their possessments in his campaigns in order to mantain peace with them.

The age of Charlemagne was therefore one of stability for Italy, though it was generally dominated by non-Italian interests. The separation with the Eastern world continued to increase. Leo III was the first Pope to date his Bulls from the year of Charlemagne's reign (795) instead of those of Byzantine emperors. This process of isolation from the Eastern Empire and connection with the Western world of France and Germany, which had started three centuries before, was completed at the beginning of the 9th centuries. Sicily, Calabria, Puglia and the marine cities were the main exceptions to this rule.

After the death of Charlemagne (814) the new empire soon disintegrated under his weak successors. The equilibrium created through the great emperor's charisma fell apart. This crisis was due also to the emergence of external forces, including the Saracen attacks and the rising power of the marine republics. Charlemagne had announced its division of the Empire in 806: the Lombard-Frank reign, together with Bavaria and Alamannia, was to be handed over to his son Pippin of Italy.

After Charlemagne's son Louis the Pious died in 840, the treaty of Verdun in 843 divided the empire. Louis' eldest surviving son Lothar I became Emperor and ruler of the Central Franks. His three sons in turn divided this kingdom between them, and Northern Italy became the Kingdom of Italy under Louis II, Holy Roman Emperor in 839.

The first half of the 9th century saw other troubles for Italy as well. In 827, Muslim Arabs known as Aghlabids invaded and conquered Sicily; their descendants, the Kalbids, ruled the island until 1053. In 846, Muslim Arabs invaded Rome, looted St. Peter's Basilica, and stole all the gold and silver in it. In response, Pope Leo IV started building the Leonine walls of the Vatican City in 847; they were completed in 853.

Most of the coastline of southern Italy was under the Eastern Roman Empire throughout the period.

Even the papacy went through an age of decadence, which ended only in 999 when emperor Otto III selected Silvester II as a pope.