Albanian-speakers of Western Thrace migrated towards today's European Turkey (Eastern Thrace), especially near Istanbul. Many Muslim Albanians achieved high office in Ottoman society and many of them, most notably the Köprülü family, became Grand Viziers of the Empire. The majority of the Albanian emigration came from Northern Kosovo and the Korça region of Albania. Descendants of this immigrants would later play an important role in the National Renaissance of Albania. The number of Albanians that resided in the region is unknown, as statistical data of the Ottoman Empire were based on religious identification (millets). Thus, the Orthodox Albanians were part of the Rûm millet,
Population exchange between Greece and Turkey Minor population. To this day, Greece and Turkey still have properties, and even villages such as Kayaköy, that have been left abandoned since the exchange. Population exchange between Greece and Turkey The 1923 population exchange between Greece and Turkey (, ) stemmed from the "Convention Concerning the Exchange of Greek and Turkish Populations" signed at Lausanne, Switzerland, on 30 January 1923, by the governments of Greece and Turkey. It involved at least 1.6 million people (1,221,489 Greeks from Asia Minor, Eastern Thrace, the Pontic Alps and the Caucasus, and 355,000 Muslims in Greece), most of whom were forcibly made refugees