It became a prominent settlement around 650 when it succeeded the ancient capital of the Roman province of Dalmatia, Salona. After the Sack of Salona by the Avars and Slavs, the fortified Palace of Diocletian was settled by the Roman refugees. Split became a Byzantine city, to later gradually drift into the sphere of the Republic of Venice and the Kingdom of Croatia, with the Byzantines retaining nominal suzerainty. For much of the High and Late Middle Ages, Split enjoyed autonomy as a free city, caught in the middle of a struggle between Venice and the King of Hungary for control over the Dalmatian cities.