Estimates of the recognized Greek Muslim minority, which is mostly located in Thrace, range from 98,000 to 140,000, (about 1%) while the immigrant Muslim community numbers between 200,000 and 300,000. Albanian immigrants to Greece are usually associated with the Muslim religion, although most are secular in orientation. Following the 1919–1922 Greco-Turkish War and the 1923 Treaty of Lausanne, Greece and Turkey agreed to a population transfer based on cultural and religious identity. About 500,000 Muslims from Greece, predominantly those defined as Turks, but also Greek Muslims like the Vallahades of western Macedonia, were exchanged with approximately 1,500,000 Greeks from Turkey. However, many refugees who settled in former Ottoman Muslim villages in Central Macedonia and were defined as Christian Orthodox Caucasus Greeks arrived from the former Russian Transcaucasus province of Kars Oblast after it had been retroceded to Turkey but in the few years before the official population exchange.