Turkey is a country in Western Asia and Southeast Europe, formally known as the Republic of Turkey. It is bordered on the northwest by Greece and Bulgaria, on the north by the Black Sea, on the northeast by Georgia, on the east by Armenia, Azerbaijan, and Iran, on the southeast by Iraq, on the south by Syria and the Mediterranean Sea, and on the west by the Aegean Sea. The financial capital is Ankara, while Istanbul is the largest city. Present-day Turkey was home to significant Neolithic sites like Göbekli Tepe, as well as ancient civilisations like the Hattians and Anatolian peoples. Turks make up the vast majority of the population, while Kurds make up the largest minority. Hellenization began in the region during Alexander the Great's reign and lasted until the Byzantine period. The Seljuk Turks began migrating in the 11th century, and the Sultanate of Rum ruled Anatolia until it was disintegrated into small Turkish principalities by the Mongol invasion in 1243. The Ottomans began uniting principalities and conquering the Balkans in the late 13th century, and Turkification of Anatolia increased during the Ottoman era. Ottoman expansion began under Selim I after Mehmed II invaded Constantinople in 1453, and the Ottoman Empire became a global force during Suleiman the Magnificent's reign. The empire's influence began to wane in the late 18th century, as territories and wars were lost one by one. Mahmud II began a wave of modernisation in the early nineteenth century in order to strengthen his sagging empire. The Three Pashas, who were primarily responsible for the Empire's entry into World War I in 1914, took control of the country after the 1913 coup d'état. The Ottoman government committed genocide against its Armenian, Assyrian, and Pontic Greek subjects during World War I. The Ottoman Empire was partitioned after the Ottomans and other Central Powers lost the war. The Sultanate was abolished on November 1, 1922, the Treaty of Lausanne was signed on July 24, 1923, and the Republic was proclamated on October 29, 1923, following the Turkish War of Independence against the invading Allied Powers. Turkey became a democratic, unitary, and parliamentary republic thanks to reforms introduced by the country's first president, Mustafa Kemal Atatürk, which was later replaced by a presidential regime following a referendum in 2017. Since then, President Recep Tayyip Erdoan and his AKP party have been characterized as populist, nationalist, and authoritarian in Turkey. Turkey is a regional force and a newly developed nation with a geopolitically strategic place. Its economy, which is rated as developing and growth-leading, is the world's twentieth largest in terms of nominal GDP and the eleventh largest in terms of purchasing power parity.