The Italian Kingdom, also known as the Kingdom of Italy or simply just Italy, is a semi-autocratic monarchy in Southern Europe, specifically centered on the eponymous Italian peninsula. It is a comparatively small, but wealthy and populated nation in Europe.
On August 23, 753, the city of Rome was founded, and with it, the Roman Kingdom. There were seven kings of Rome, the last one, Tarquinius Superbus, was overthrown in a revolt sparked by his son's raping of an important noblewoman, Lucretia. The Romans subsequently established an oligarchic republic.
Italy, over the years, would be unified and consolidated by the Romans and they began expanding outwards. These conquests, spearheaded by historical figures such as Gaius Julius Caesar, would forge a Roman State stretching from Britan to Egypt. The Roman Empire was proclaimed in 27 BC, under the reign of Augustus and two centuries of tranquility and prosperity ensued, a period regarded as the Pax Romana. Following the reign of Commodus, the Roman Empire slumped into decline, and in 395, Emperor Theodosius split the empire in half, the Western Roman Empire, and the Eastern Roman Empire. The West fell into rapid decline and upheaval and in 476, Romulus Augustus, the final Western Roman Emperor, was deposed.
After the fall of the Western Roman Empire, Italy fell under the power of Odoacer's kingdom, and, later, was seized by the Ostrogoths, followed in the 6th century by a brief reconquest under Byzantine Emperor Justinian. The invasion of another Germanic tribe, the Lombards, late in the same century, reduced the Byzantine presence to the rump realm of the Exarchate of Ravenna and started the end of the political unity of the peninsula for the next 700 years. Invasions of the peninsula caused a chaotic succession of barbarian kingdoms and the so-called "dark ages". The Lombard kingdom was subsequently absorbed into the Frankish Empire by Charlemagne in the late 8th century. The Franks also helped the formation of the Papal States in central Italy. Until the 13th century, Italian politics was dominated by the relations between the Holy Roman Emperors and the Papacy (or alternatively, the Byzantines).
Point of Divergence (1189)
In TTL, in 1189, Fredrick Barbarossa invaded Northern Italy, engaging the Papal-backed Lombard Leauge and defeating them at the Battle of Pavia in 1190. This took the meat out of the Papal coalition that had formed during the Investiture Controversy, isolating the Pope in his territorial holdings in central Italy. This would later allow for Fredrick to march into Rome, installing his anti-pope and paving the way for full Imperial control of Italy once more, as well as also providing wealth for him and his descendants to eliminate the constant revolts in Northern Germany. This would allow for the Holy Roman Empire to remain as a large, centralized, and united force.