original_query: What was the reason behind the population exchange between Greece and Turkey in 1923?
query: What was the reason behind the population exchange between Greece and Turkey in 1923?
answer: The population exchange between Greece and Turkey in 1923 was a result of the Treaty of Lausanne, which ended the Greco-Turkish War.  The exchange was based on religious grounds, with roughly 1.5 million Greeks leaving Turkey for Greece and about half a million Turks leaving Greece for Turkey (Christians for Muslims).  Exceptions were made for Istanbul and some islands.