Two of the island’s many sheltered bays have so far yielded substantial evidence of prehistoric settlement and trade of the 4th millennium bc. Finds of obsidian, of a kind that comes from both nearby Giali (Nisyros), and of a purer form from Milos in the Western Aegean, show that the material was fashioned in workshops on Leros (in the area of Drymonas) and that there was therefore frequent long distance trade by sea between these islands in this early period. Little trace of Minoan or Mycenean artefacts has been found, however, even though there was a significant Minoan trading presence at Miletus on the coast opposite.
In early historic times Leros was an Ionian island whereas Kalymnos, and its southern neighbours as far as Rhodes , were Dorian. Leros and Kalymnos almost touch and are even referred to by the same general name—the ‘Calydnian Islands’—by Homer in the Iliad; but their histories and cultures are separate. Leros was influenced by, fortified by, written about by, and settled by people from Miletus, one of the greatest of the Ionian cities in the 6th century bc. Phokylides of Miletus, a poet of this period, refers to the island somewhat derisorily in an epigram; and Herodotus, in talking about the Ionian revolt of 498 bc (Hist. V. 125), mentions that Leros was suggested to Aristagoras, Tyrant of Miletus, as a safe refuge which it was worth his fortifying well, against the possibility of his being forced to flee from Miletus. Athenian tribute lists of 454/453 bc also refer to Milesians ‘from Leros’. By the 4th century bc, Leros appears as a deme of Miletus. The 6th century bc philosopher, Demodikos, and the later Hellenistic historian, Pherekydes, were both from Leros: the latter’s history of the island is lost, depriving us of valuable information on the subject. The main settlement on the is land in Antiquity—continuously inhabited from Geometric through to Roman and Early Christian times—was at the southeast corner of Alinda Bay; the principal religious centre was the sanctuary of Artemis, or Parthenos Iokallis, in Partheni Bay. Early Christian basilicas were built at both of these sites as well as at several other places on the island attesting to a large and well-established Christian community. A bishop of Leros is first mentioned as present at the Fifth Ecumenical Council of Constantinople in 553 ad.
Against opposition from the islanders, the fertile lands at Temenia (east of Lakki) and around Partheni, and a portion of the fortress of Pandeli, were all given by the Byzantine Emperor, Alexius I Comnenus, in 1088 to Hosios Christodoulos to be a revenue for the monastery of St John on Patmos. Together with Rhodes and Kos, Leros was acquired by the Knights of St John in 1309, who strengthened and considerably enlarged the existing Byzantine castle in the course of the next century. In 1523 it became a Turkish possession after the defeat of the Knights of Rhodes by the Ottoman Sultan, Suleiman the Magnificent. It was taken briefly by the Venetian Admiral, Leonardo Foscolo, in 1648 during hostilities between Turkey and Venice.
Leros generally enjoyed a measure of independence under Ottoman rule; this gave it the possibility to participate actively in the War of Independence in 1821; in 1830 it briefly had a local Greek Governor as part of the new Greek State, but returned under Ottoman rule again through the terms of the London Protocol of the same year. In the fol lowing decades of the 19th century, there was an important and rich community of intellectuals and businessmen who had emigrated to Egypt from Leros, and who were to become important benefactors of the island’s architecture, art collections, schools and institutions. During the Italian Occupation of the Dodecanese (1912–43) Leros was transformed by the avant-garde building projects of the new ‘Porto Lago’ (Lakki) area. The island was the scene of fierce fighting in the Second World War, culminating in the Battle of Leros in November 1943 (see below), when it was taken by German forces. It joined the Greek State in 1948 together with all the Dodecanese Islands. The substantial legacy of military buildings on Leros was used for confining political prisoners during the period of the Colonels’ Junta (1967–74), and thereafter others were used as a National Mental Institution. Between 1989 and 1995 this was the object of a European Union inquest into maladministration of funds and maltreatment of patients. Substantial improvements in conditions and the opening of a large nursing school in 1999 have helped to put the worst period behind.
Leros Island is part of the Dodecanese Island Group, Greece.