Around AD 639 the hinterland of Dalmatia fell after the invasion of Avars and Slavs, and the city of Salona was sacked. The majority of the displaced citizens fled by sea to the nearby Adriatic islands. Following the return of Byzantine rule to the area, the Roman population returned to the mainland under the leadership of the nobleman known as Severus the Great. They chose to inhabit Diocletian's Palace in Spalatum, because of its strong fortifications and defendable setting. The palace had been long-deserted by this time, and the interior was converted into a city by the Salona refugees, rendering Spalatum the effective capital of the Province.