I'm about to summarize nearly one thousand years of history. Fasten your seat belt.

Part I: The First Kingdom of Italy

Let's begin at the beginning. The year is 476. The Western Roman Empire has lost Gaul (to the Franks) Iberia (to the Visigoths) and Africa (to the Vandals). Only Italy and Dalmatia continues to be ruled by Rome. Years of civil wars an infighting has decimated the army, and a long succession of army-backed strongmen have taken turns ruling the empire, many of whom have mixed heritage; Romulus Augustulus, the last emperor, was himself was a puppet of his father Orestes, who was the Magister Militum (head of the army) and although he had married into a Roman family, he himself was not an ethnic Roman (to be pedantic, the Eastern Emperor never even recognized Augustulus, which allowed Julius Nepos, the pervious emperor, to rule in semi-autonomy in Dalmatia claiming all the while to be Emperor of the West).

Flavius Odoacer, the de facto leader of the Foederati or ethnic "Barbarians" fighting for Rome (who made up most of the army), deposed Romulus Augustulus when he lost the army's favor. Odoacer then openly admitted that although he might rule Italy, he was powerless beyond the alps, and didn't call himself Emperor, rather, he sent the imperial paraphernalia to Constantinople and asked to be recognized as "Consul", keeping all of the functions of the Roman Administration in Italy intact (understandable, Flavius Odoacer as was so romanized historians aren't sure which "Barbarian" ethnic group he belonged to). He initially played lip service to the pervious emperor Julius Nepos, minting coinage in his name, but may have been involved in the plot whereby he was murdered. Regardless, after the murder of Julius Nepos, Odoacer asked to be given the title of Patrician by the Eastern Emperor, and be recognized as the ruler of Italy under the wing of a single Roman Emperor in Costantinople.

The Eastern Emperor Zeno, however, had his own issues to deal with involving "Barbarian Generals", namely involving two Ostrogoths, both confusingly named Theodoric (this in addition to social, religious, and political unrest in his own half of the empire).

Although the Ostrogoths had been given lands in Pannonia in exchange for the defense of the upper Danube, Zeno came to the conclusion that the Ostrogoths were more trouble than they were worth (fighting with him, fighting with each other, and in a general sense just being another annoying thing to have to deal with) so he convinced them to go conquer Italy. This way, they would stop annoying him, and he could also get rid of Odoacer, at this point another potential opponent.

Theodoric the Amal, King of the Ostrogoths, had been raised in Constantinople. His people were largely Romanized, having lived within the Eastern Empire's borders for centuries. When he defeated Odoacer and set up the first Kingdom of Italy, he did his utmost to further maintain the Roman institutions, law, and judicial system. However, he did not rule from Rome, rather, he ruled from Ravenna, seaside city conveniently defended by swampy surroundings, and easily supplied by ship.

Although Theodoric was de jure a vassal of the Eastern Roman Emperor, de facto the Kingdom of Italy operated entirely independently. (I suggest this book every time Theodoric comes up, he was awesome: Theoderic in Italy by J. Moorhead (Oxford University Press, Oxford, 1992).