History of Europe
In 395 Theodosius I, who had made Christianity the official religion of the Roman Empire, would be the last emperor to preside over a united Roman Empire. The empire was split into two halves: the Western Roman Empire centred in Ravenna, and the Eastern Roman Empire (later to be referred to as the Byzantine Empire) centred in Constantinople. The Roman Empire was repeatedly attacked by Hunnic, Germanic, Slavic and other “barbarian” tribes (see: Migration Period), and in 476 finally the Western part fell to the Heruli chieftain Odoacer.
History of Split
The Palace was to have one further significant occupant, however: Flavius Julius Nepos, the last legitimate Emperor of the Western Roman Empire. By the late 5th century CE, the Western provinces of the Empire fell under the control of various Germanic confederations. Dalmatia (which had been considered a Western province since the reign of Theodosius I) eventually remained the only exception in that regard. From 468 CE, the Province was ruled by Julius Nepos, who was appointed Western Emperor in 473 CE by Leo I of the Eastern Court. He attempted to establish himself in the Western capital of Ravenna (right across the Adriatic from Salona), but was deposed within two years by his Germanic "Magister militum", Orestes. He returned to Salona in 475 and took Diocletian's Palace for his residence. Orestes installed his young son Romulus Augustulus as the Emperor in the West, but was murdered within a year (476 CE) by Odoacer and his son deposed. Thereupon Odoacer did not establish his own puppet emperor, but instead returned the Imperial regalia of the West to the Emperor in the East (that now being Emperor Zeno), effectively abolishing the Western Imperial throne. The Eastern Court in Constantinople, however, still recognized Julius Nepos as legitimate Western Emperor. From AD 475, Nepos therefore ruled from Diocletian's Palace as effective "Emperor of Dalmatia". He was however murdered in the Palace by local political enemies in 480 CE, whereupon the two thrones of the Roman Empire were formally united under the Eastern emperors in Constantinople, who now became the sole Roman emperors. The Empire itself is henceforward more commonly referred to in historiography as the Byzantine Empire.
In 493 CE Salona, along with most of Dalmatia, was lost to the Ostrogothic Kingdom. However, by 535 CE the Emperor Justinian the Great was ready to attempt a reconquest of Roman lands held by the Ostrogoths. By July of the same year, the Roman general Mundus had quickly overrun Dalmatia and captured Salona. But a large Gothic army arrived to reclaim the province, and though he inflicted a heavy defeat upon them, Mundus himself was mortally wounded. As a result, the Roman army withdrew, and all of Dalmatia, with the exception of Salona, was abandoned to the Goths. Salona was then taken by the Gothic general Gripas. Justinian dispatched a new general, Constantianus, to recover Dalmatia, which he accomplished speedily. Gripas was forced to abandon Salona because of the ruined state of its fortifications and the pro-Roman stance of its citizens. Constantinianus then occupied the city and rebuilt its walls. Seven days later, the Gothic army departed for Italy, so that by late June 536 CE Dalmatia was again in Roman hands.