İsmet İnönü became Turkey’s second President following Atatürk’s death on 10 November 1938. On 29 June 1939, the Republic of Hatay voted in favor of joining Turkey with a referendum. Turkey remained neutral during most of World War II, but entered the closing stages of the war on the side of the Allies on 23 February 1945. On 26 June 1945, Turkey became a charter member of the United Nations. In the following year, the single-party period in Turkey came to an end, with the first multiparty elections in 1946. In 1950 Turkey became a member of the Council of Europe.
The Democratic Party established by Celâl Bayar won the 1950, 1954 and 1957 general elections and stayed in power for a decade, with Adnan Menderes as the Prime Minister and Bayar as the President. After fighting as part of the United Nations forces in the Korean War, Turkey joined NATO in 1952, becoming a bulwark against Soviet expansion into the Mediterranean. Turkey subsequently became a founding member of the OECD in 1961, and an associate member of the EEC in 1963.
The country’s tumultuous transition to multiparty democracy was interrupted by military coups d’état in 1960 and 1980, as well as by military memorandums in 1971 and 1997. Between 1960 and the end of the 20th century, the prominent leaders in Turkish politics who achieved multiple election victories were Süleyman Demirel, Bülent Ecevit and Turgut Özal.
Following a decade of Cypriot intercommunal violence and the coup in Cyprus on 15 July 1974 staged by the EOKA B paramilitary organization, which overthrew President Makarios and installed the pro-Enosis (union with Greece) Nikos Sampson as dictator, Turkey invaded Cyprus on 20 July 1974 by unilaterally exercising Article IV in the Treaty of Guarantee (1960), but without restoring the status quo ante at the end of the military operation. In 1983 the Turkish Republic of Northern Cyprus, which is recognized only by Turkey, was established. The Annan Plan for reunifying the island was supported by the majority of Turkish Cypriots, but rejected by the majority of Greek Cypriots, in separate referendums in 2004. However, negotiations for solving the Cyprus dispute are still ongoing between Turkish Cypriot and Greek Cypriot political leaders.
The conflict between Turkey and the PKK (designated a terrorist organisation by Turkey, the United States, the European Union and NATO) has been active since 1984, primarily in the southeast of the country. More than 40,000 people have died as a result of the conflict. In 1999 PKK’s founder Abdullah Öcalan was arrested and sentenced for terrorism and treason charges. In the past, various Kurdish groups have unsuccessfully sought separation from Turkey to create an independent Kurdish state, while others have more recently pursued provincial autonomy and greater political and cultural rights for Kurds in Turkey. In the 21st century some reforms have taken place to improve the cultural rights of ethnic minorities in Turkey, such as the establishment of TRT Kurdî, TRT Arabi and TRT Avaz by the TRT.
Since the liberalization of the Turkish economy in the 1980s, the country has enjoyed stronger economic growth and greater political stability. Turkey applied for full membership of the EEC in 1987, joined the EU Customs Union in 1995 and started accession negotiations with the European Union in 2005. In a non-binding vote on 13 March 2019, the European Parliament called on the EU governments to suspend EU accession talks with Turkey, citing violations of human rights and the rule of law; but the negotiations, effectively on hold since 2018, remain active as of 2020.