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,
Turks of Western Thrace province of East Macedonia and Thrace. However, the Greek language is also widely used. Article 37 through 45 of the Lausanne Treaty set forth the obligations of the Greek and Turkish governments to protect the Turkish and Greek minorities in their territories. Each country agreed to provide the following: The Lausanne Treaty defined the rights of the Muslim communities in Western Thrace, on the basis of religion, not ethnicity, as well as maintained a balance between the minority communities of both countries (Turks in Greece and Greeks in Turkey) on reciprocal obligations toward each of those minorities. The Treaty contained