The Republic of Turkey was proclaimed in 1923, with Kemal Atatürk as its first president. Far-reaching political, social, and economic reforms were put into effect. Atatürk abolished the sultanate and later exiled all Ottoman heirs. He did away with old traditions associated with the empire—men could no longer wear the fez (a hat), nor women the veil. Women were given political and civil rights equal to those of men. Church and state were separated, and the property of the mosques nationalized. Universal education and a new law code were introduced. When many of these changes were not accepted by the people, Atatürk assumed unlimited dictatorial powers. After his death in 1938, the premier, Ismet Inönü, was elected president.

By the Montreux Convention of 1936, Turkey was given the right to fortify the Dardanelles and Bosporus straits. Treaties of alliance were signed with Great Britain and France in 1939. During World War II, Turkey remained neutral until 1944, when it broke relations with Germany. The following year, it declared war on Germany and Japan.