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,
Immigration to Turkey enter through the Eastern border, which generally included all Iranians and Afghans who entered illegally. In 1923, more than half a million ethnic Muslims of various nationalities arrived from Greece as part of the population transfer between Greece and Turkey (the population exchange was not based on ethnicity, but by religious affiliation; as Turkey was seen as a Muslim country while Greece was viewed as a Christian country). After 1925, Turkey continued to accept Turkic-speaking Muslims as immigrants and did not discourage the emigration of members of non-Turkic minorities. More than 90% of all immigrants arrived from the Balkan countries.