Italy seized the Dodecanese, including the larger island of Rhodes, during the Italo-Turkish War of 1911-12. The Treaty of Ouchy, which ended that war, called for Italy to return the islands, but was vague enough that Italy held onto the islands.

After World War I, the Treaty of Sevres between the Ottomans and the victorious Entente powers called for Italy to return the Dodecanese to Greece (except for Rhodes). In return, the Italians inserted a clause in the treaty which gave them a sphere of influence in southwestern Turkey covering a quarter of Anatolia.

The Turkish War of Independence which followed ended in the defeat of Greece and smaller contingents from the other Entente powers. When Italy lost its sphere of influence in the 1923 Treaty of Lausanne between the Entente and the new Republic of Turkey, it held onto the Dodecanese. (Turkey renounced its claim on the islands in the same treaty.)

The new Fascist government of Mussolini tightened its grip on Rhodes, intending to make it the center of a new Italianization campaign should it ever conquer Greece and regain a foothold in Turkey. It spent a lot of money trying to modernize its Aegean colony, banned Orthodox services, and switched the schools from Greek to Italian. The inhabitants of the islands, who were overwhelmingly Greek even after 30 years of Italian colonization efforts, were understandably happy when the islands were annexed to Greece in 1947.