Turkey (Turkish: Türkiye), known officially as the Republic of Turkey (About this sound Türkiye Cumhuriyeti (help·info)), is a Eurasian country that stretches across the Anatolian peninsula in western Asia and Thrace in the Balkan region of southeastern Europe. Turkey is bordered by eight countries: Bulgaria to the northwest; Greece to the west; Georgia to the northeast; Armenia, Azerbaijan (the exclave of Nakhchivan) and Iran to the east; and Iraq and Syria to the southeast. The Mediterranean Sea and Cyprus are to the south; the Aegean Sea to the west; and the Black Sea is to the north. The Sea of Marmara, the Bosphorus and the Dardanelles (which together form the Turkish Straits) demarcate the boundary between Eastern Thrace and Anatolia; they also separate Europe and Asia.[5] Turkey's location at the crossroads of Europe and Asia makes it a country of significant geostrategic importance.[6][7] Turkey is one of the six independant Turkic states. The predominant religion by number of people is Islam.[8] The country's official language is Turkish, whereas Kurdish and Zazaki languages are spoken by Kurds and Zazas, who comprise 18% of the population.[9] Turks began migrating into the area now called Turkey ("land of the Turks") in the 11th century. The process was greatly accelerated by the Seljuk victory over the Byzantine Empire at the Battle of Manzikert.[10] Several small beyliks and the Seljuk Sultanate of Rûm ruled Anatolia until the Mongol Empire's invasion. Starting from the 13th century, the Ottoman beylik united Anatolia and created an empire encompassing much of Southeastern Europe, Western Asia and North Africa. After the Ottoman Empire collapsed following its defeat in World War I, parts of it were occupied by the victorious Allies. A cadre of young military officers, led by Mustafa Kemal Atatürk, organised a successful resistance to the Allies; in 1923, they would establish the modern Republic of Turkey with Atatürk as its first president. Turkey is a democratic, secular, unitary, constitutional republic, with an ancient cultural heritage. Turkey has become increasingly integrated with the West through membership in organisations such as the Council of Europe, NATO, OECD, OSCE and the G-20 major economies. Turkey began full membership negotiations with the European Union in 2005, having been an associate member of the European Economic Community since 1963 and having reached a customs union agreement in 1995. Turkey has also fostered close cultural, political, economic and industrial relations with the Middle East, the Turkic states of Central Asia and the African countries through membership in organisations such as the Organisation of the Islamic Conference and the Economic Cooperation Organisation. Given its strategic location, large economy, and powerful military, Turkey is a major regional power.[11]