Millions of Kurds fled across the mountains to Turkey and Kurdish areas of Iran during the Gulf War. Big Excursion, 1988-1994 The "Big Excursion" was, until the Syrian refugee crisis of 2011, was the most recent immigration influx, and primarily concerned Bulgarian Turks and Bosnian Muslims. In 1989, an estimated 320,000 Bulgarian Turks fled to Turkey to escape a campaign of forced assimilation. Following the collapse of Communism in Bulgaria, the number of Bulgarian Turks seeking refuge in Turkey declined to fewer than 1,000 per month. In fact, the number of Bulgarian Turks who voluntarily repatriated (125,000) actually exceeded new arrivals from the country. By March 1994, a total of 245,000 Bulgarian Turks had been granted Turkish citizenship. However, Turkey no longer regards Bulgarian Turks as refugees. Beginning in 1994, new entrants to Turkey have been detained and deported. As of December 31, 1994, an estimated 20,000 Bosniaks were living in Turkey, mostly in the Istanbul area. About 2,600 were living in camps, the rest were dispersed in private residences. More recent estimates put the number of Bosniaks in Turkey at 3 to 5 million. Turkey's Migration Crisis Turkey's migrant crisis or Turkey's refugee crisis is a period during the 2010s characterized by high numbers of people arriving in Turkey. As reported by UNHCR in 2018, Turkey is hosting 63.4% of all the refugees (from the Middle East, Africa, and Afghanistan) in the world. As of 2019, Refugees of the Syrian Civil War in Turkey (3.6 million) are the highest "registered" refugees. Turkey has traditionally been a major transit port for illegal immigrants to enter the European Union, but as Turkey has grown in wealth, it now finds itself a major focal point in illegal immigration. Citizenship Turkish nationality law is based primarily on the principle of jus sanguinis. Children who are born to a Turkish mother or a Turkish father (in or out of marriage) are Turkish citizens from birth. The intention to renounce Turkish citizenship (or acquire citizenship from another state) is submitted in Turkey by a petition to the highest administrative official in the concerned person's place of residence, and when overseas to the Turkish consulate. Documents processed by these authorities are forwarded to the Ministry of Interior (Turkey) for appropriate action. Turkey Citizenship by Investment Program In 2016, Turkey implemented a Golden Visa program that allows foreign investors to obtain a Turkish passport typically within six