Empire. Emperor Diocletian built a large palace in Split when he retired in AD 305. During the 5th century, one of the last Emperors of the Western Roman Empire, Julius Nepos, ruled his small empire from the palace. The period ends with Avar and Croat invasions in the first half of the 7th century and destruction of almost all Roman towns. Roman survivors retreated to more favourable sites on the coast, islands and mountains. The city of Dubrovnik was founded by such survivors from Epidaurum.
The ethnogenesis of Croats is uncertain and there are several competing theories, Slavic and Iranian being the most frequently put forward. The most widely accepted of these, the Slavic theory, proposes migration of White Croats from the territory of White Croatia during the Migration Period. Conversely, the Iranian theory proposes Iranian origin, based on Tanais Tablets containing Greek inscription of given names Χορούαθ[ος], Χοροάθος and Χορόαθος (Khoroúathos, Khoroáthos, and Khoróathos) and their interpretation as anthroponyms of Croatian people.
Middle Ages
According to the work De Administrando Imperio written by the 10th-century Byzantine Emperor Constantine VII, the Croats had arrived in what is today Croatia in the early 7th century, however that claim is disputed and competing hypotheses date the event between the 6th and the 9th centuries. Eventually two dukedoms were formed—Duchy of Pannonia and Duchy of Dalmatia, ruled by Ljudevit Posavski and Borna, as attested by chronicles of Einhard starting in the year 818. The record represents the first document of Croatian realms, vassal states of Francia at the time. The Frankish overlordship ended during the reign of Mislav two decades later. According to the Constantine VII christianization of Croats began in the 7th century, but the claim is disputed and generally christianization is associated with the 9th century. The first native Croatian ruler recognised by
