In the 6th century it came under Byzantine rule. The Great Migrations of the 6th and 7th centuries brought Croatian invasions into this region. Along the Dalmatian coast the Croatian peoples poured out of the interior and seized control of the area where the Neretva River enters the Adriatic, as well as the island of Korčula (Corcyra), which protects the river mouth. The Christianisation of the Croats began in the 9th century, but the early Croatian rural inhabitants of the island may well have fully accepted Christianity only later; in the early Middle Ages the Croatian population of the island was grouped with the pagan Narentines or Neretvians, who quickly learned maritime skills in this new environment and became known as pirates.