Historically, Amorgos was one of the most important centres of the Cycladian civilisation. Like the rest of the Cyclades, it was under the sway of Crete. Egiali and Arkesini were founded by Naxiot colonists. During the 5th century BC, Amorgos joined the Athenian League. In the Hellenistic era, it was taken by the Ptolemies of Egypt. Afterwards, it fell into the possession of the Romans who used it as an exile. In 1207 the island was conquered by the Venetians, who gave it to the Duchy of Naxos. It was ruled by several royal Venetian and Frankish families. In 1537, it was ransacked repeatedly by pirates and many Naxiots sought refuge in Naxos and Crete. Amorgos took an active part in the Greek War of Independence of 1821 and was finally liberated in 1830 by the Treaty of London.