In 1925, Atatürk (1881–1938) – here on a visit to Izmir – introduced the so-called Hat Law (Turk. Şapka kanunu). This reform or revolutionary law determined that the hat was the head covering for the male population and at the same time forbade the wearing of the oriental head coverings. The law is in force de jure to this day.
Mustafa Kemal in Izmir for the campaign of the Hat Revolution, October 11, 1925; black-and-white photography, 1925, photographer: NA, source: Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Hat_Law_Izmir.jpg, public domain.