The island was inhabited even as early as 2000 BC. Colonists from Thera founded the city of Cyrene in Africa. In the fifth century BC, during the Peloponesian war, Thera and Milo were the only two island-states that denied the alliance with Athens. The island became a naval base for the Ptolemaic dynasty during the Hellenistic years. In the early decades of the twentieth century, the island was used as a place of exile for political prisoners. It was "discovered" again, by tourists, in the first two decades that followed World War II and ever since then the island has evolved into a major attraction for the majority of the visitors that come to Greece every year.