East Thrace the Turkish Straits) and the Sea of Marmara, a route of about 361 km. The southernmost part of Eastern Thrace is called the Gallipoli peninsula. European Turkey is bordered on the west by Greece for 212 km and on the north by Bulgaria for 269 km, with the Aegean Sea to the south-west and the Black Sea to the north-east. East Thrace was the setting for several important events in history and legend. The mass killings and displacement of Thracian Bulgarians in 1913 and the 1923 population exchange between Greece and Turkey ethnically cleansed the Orthodox populations. Prior to that
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.