The Ostrogothic throne then passed to Thoedoric's grandson Athalric, a child. His mother Amalasuntha became a powerful regent. Still Romanist in intent, they elevated Cassiodorus to Praetorian Prefect. Athalric died in 534, however, and Ostrogothic nobles were unprepared to tolerate female rule, especially as she continued Romanization. They thus nominated Theodoric's nephew Theodehad as king, who after marrying Amalasuntha, imprisoned her. According to official Byzantine sources, she had been assured by Justinian of imperial protection, and after her murder in 535, the Emperor had came close to effecting Theodehad's (also a Romanizer) abdication in favor of himself. A preemptive Gothic strike against Dalmatia during which a close associate of the Emperor was killed however, ended negotiations. Using recently re-conquered ex- Vandal North Africa as a base, Justinian's general Belisarius invaded Sicily, occupying it quickly (535), then proceeded to take Naples. Advancing north, Belisarius found only sporadic resistance, and was able to take Rome in 537. By this point, regrouped Goths had elected a new king, Wittigis, who was able to besiege the Byzantine commander in the city. In the following year, a second Byzantine army had landed in the Italian north, cutting off Wittigis' communications with his capital in Ravenna. A year later, Belisarius had broken out of Rome and chased dispiritied Goths back to Ravenna, where he was able to besiege Wittigis. By 540 a land and naval blockade of the city convinced the Goths to negotiate. Holding out the possibility that he would revolt against Constantinople and declare himself western emperor, Belisarius tricked the Ostrogoths into surrendering the city. Thus, by 540, Italy had been regained by a resurgent Empire.
The tide turned just as immediately. Just prior to defeat, Wittigis had appealed to the Persian Sassanian shah Chosroes II for help in the form of opening a second front along Byzantium's eastern borders. This he did, and in 540, marched as far as Antioch (along the modern Syrian-Turkish border), sacking the important Christian city and carrying off its survivors. Justinian thus ordered Belisarius to the East, with Goths as added soldiers. Under a new Gothic king elected in Pavia, the second phase of the Italian war began, lasting from 540-552. The king's nephew, Totila, guaranteed a bloody, drawn out, quite expensive contest. He was finally defeated by Belisarius' replacement Narses at Busta Gallorum (552), while his successor Teias was defeated the following year.
By this point, other European powers had taken an interest in Italy. From the late 530s, Franks began encroaching southward, looting Milan in 539, and holding Venetian areas until the mid 550s. Any semblance of a great Roman revanche in Italy was ended in 568, when the solidly Barbarian and savage Lombards, who had been permitted entry into Pannonia by Justinian himself, descended upon Italy, bypassing cities and ravaging rural areas. Their king Alboin had himself crowned in Milan in 569, while by 573-4 he was able to occupy Pavia, which became their capital. In the next twenty years, Lombards lived without kings, with up to thirty-six dukes sharing power to pillage and extend Lombard control as far south as Apulia. They had no interest in unification or Roman traditions. By 600, three powers vied in Italy: the Lombards, in control from the Frankish north through the majority of the Italian boot; Byzantium, which controlled the environs of Rome, connected to Ravenna's precincts by a small corridor, Otranto and Apulia, as well as Sicily, Sardinia, and the boot of Italy; and the Papacy, which while supporting the Byzantines, shouldered much civil administration, and was looking to other patrons in the face of receding Byzantine protection against the Lombards.
Looking at the 470-600 period, four primary questions present themselves: 1) Did Roman civilization fall with the arrival of the Ostrogoths? 2) Why was Theodoric not able to engineer a lasting political arrangement? 3) Why did Justinian's reconquest prove so ephemeral? 4) What made the Lombard invasion of Italy so different from previous Barbarian incursions? Regarding the first matter, while it is true that Rome as a united polity ceased to exist really from the 450s, it can be argued that Theodoric at least was consciously attempting to establish a Roman continuity, now under Gothic political control. It was of course, important that he have freedom of action from Eastern Roman interference; still, he presented himself in earnest only as Zeno's viceroy, and maintained proper relations with Constantinople. He also restored much of Rome's urban landscape, recommenced the dole, and continued to nominate senators from the historically prominent families such as the Cassiadori, of course forwarding their names to Constantinople for approval.
While this could all be interpreted as simply practical, a more substantive element must be considered. Theodoric's people, whether long-term Ostrogoths or the newer accretions to the tribe, had interacted with Rome as a state and culture since the 360s. Among the masses of Barbarians, they and the Visigoths were the most highly Romanized, and most familiar with what they had come to possess. While on the one hand they were committed to their Germanness and its accoutrement--such as Arainism, tribal justice, and personal bonds of loyalty and legal strictures--many of the leading Ostrogoths were equally committed to becoming part of Rome, or at the least, making Rome theirs. This did not involve eliminating previous elites. They were of course necessary to aid the newcomers in accomplishing their goals. Just as certainly, individuals such as Symmachus, Boethius, and Cassiodorus were aware of the niche they could fill and the ways they could facilitate a continuity of civilization as they knew it. Indeed, chroniclers put into Theodoric's mouth the notion that while the Germans had come with the martial spirit and civic energy the urbanized Romans had lost over the previous centuries, the Romans themselves would contribute knowledge of administration, culture, and the arts. Thus, a new synthesis would guarantee Roman continuity.
Given this, why did Theodoric's plan fail? Part of it is due to the fact that the idea was not thoroughgoing synthesis as such, where both elements undergo something of a metamorphosis. In key spheres necessary for melding, Goths and Romans were kept separate. Religion and law were essential here. Western Romans simply would not regard Arian Christians as being of the same confessional group as they were. And, as the Ostrogothic leaders felt pressured from Orthodox Constantinople or newly Catholic Franks, it was too easy for them to perceive a need to restrict Catholic expression in Italy. As regards law, Threodoric was simply unable to convince his Goths to submit to indigenous Roman courts, procedure, or legal principles. As was the case in their attitude to Ariansim, for the Germans, giving up the wergild and ordeal system was analogous to surrendering national identity. What evolved then was de facto--or perhaps de jure--segregation on ethnic lines in almost all areas that could have united two peoples yearning for stability.