The occupation of Constantinople and Smyrna by the Allies in the aftermath of World War I prompted the establishment of the Turkish national movement.Under the leadership of Mustafa Kemal Pasha, a military commander who had distinguished himself during the Battle of Gallipoliin World War 1, the Turkish War of Independence was waged with the aim of revoking the terms of the Treaty of Sèvres.
By 18 September 1922, the occupying armies were expelled, and the Ankara-based Turkish regime, which declared itself the legitimate government of the country in April 1920, started to formalize the legal transition from the old Ottoman Empire into the new Republican political system. On 1 November, the newly founded parliament formally abolished the Sultanate, thus ending 623 years of Ottoman rule. The Treaty of Lausanne of 24 July 1923 led to the international recognition of the sovereignty of the newly formed "Republic of Turkey" as the continuing state of the Ottoman Empire, and the republic was officially proclaimed on 29 October 1923 in Ankara, the country's new capital. The Lausanne treaty stipulated a population exchange between Greece and Turkey, whereby 1.1 million Greeks left Turkey for Greece in exchange for 380,000 Turks transferred from Greece to Turkey.
Mustafa Kemal became the republic's first President and subsequently introduced many radical reforms with the aim of transforming old Ottoman-Turkish state into a new secular republic.With the Surname Law of 1934, the Turkish Parliament bestowed upon Mustafa Kemal the honorific surname "Atatürk" (Father of the Turks.)