Every regime bases itself on some sort of legitimacy. This basis makes it reasonable, reliable and entitled to be supported, and in sum, legitimate. At the beginning, the Turkish Republic faced such a problem of legitimacy. In the early 20th century, Turkey was a new state that had recently adopted the republican regime, and it was established on the last remnants of the Ottoman Empire.
Mustafa Kemal [Atatürk] and his friends had no intention of maintaining the Ottoman Empire on the 800,000 square kilometers of land left behind, and perhaps, their initial desire was to design a nation-based state within the borders of the National Pact (Misak-ı Milli) -- which roughly correspond to the current borders of the country -- instead of an Ottoman Empire with its traditional institutions such as the sultanate and the caliphate, which had been done away with. In an interview he gave to Abdi İpekçi, Sadi Irmak says Atatürk had divulged this idea to the British in 1907.
Every nation-state in the world adopts an isolationist attitude against universal and multicultural states that adopt religion as a founding philosophy. The problem faced by every nation-state was faced by the Turkish Republic, which, like others, rejected the pluralistic, sociocultural and political structure of the multi-congressional and multiethnic Ottoman Empire. To this can be added other missions such as modernizing the society.
Departing from this, republicans picked up internal and external enemies at the beginning. Thus, their internal enemy was Islam, i.e., the religious lifestyle of the people, while their external enemy was Greece. This was how the bases of legitimacy were established for the new republic. However, in 1925, Şeyh Said revolted, citing objections to the exclusion of Islam from the system and to the efforts to Turkify Kurds, among others, and republicans added the ethnic and unique cultural presence of Kurds as another internal enemy. Even without this revolt, those who founded the nation-state based on the Turkish ethnic identity would still refuse to accept the Kurdish presence.
You can guest more or less what happened next. The Independence Tribunals (İstiklal Mahkemeleri), established under the Law on the Reinstatement of Public Order (Takrir-i Sükun), passed after Sheikh Said’s revolt, rushed to repress the regime’s opponents, and this also served as a good opportunity for the authorities to ensure that the new regime, i.e., an authoritarian oppressive administration, could be planted firmly and branch out.
Today, everyone knows that Turkish republicans had undertaken practices as atrocious as those committed by French republicans. First, the people with increased religious awareness were subjected to the most ruthless form of oppression. During this long period of oppression --corresponding to the 27 years of the single-party era between 1923 and 1950 -- Muslims were stripped of the most basic rights and freedoms. Thousands of people were killed or displaced or jailed. Moreover, as a cruelty unrivaled in history, the call to prayer (ezan) was changed from Arabic to Turkish in 1932, and some mosques were used as stables, etc. All these tyrannical practices and violations of law had left their marks deep in the hearts of the people who took their religious lives seriously.
This historical background, which still gives people shudders when recalled, made fear a dominant emotion among Muslims. Of course, these pious people mainly consisted of the weak masses. Indeed, elite Muslims scholars and leaders had been martyred during the wars -- the Balkan wars, World War I and the Çanakkale wars, in which about 250,000 people died and which is also called the War of Madrasah Graduates since about 50,000 madrasah and school graduates were martyred, most of whom were the sacrificial Islamists who promoted the revival of the Muslim word. Those who were spared in these wars were done away with by the Independence Tribunals. So what was left behind consisted of women, children, the elderly and those who would not care about political developments, and they were deprived of any strength or power to voice opposition.
As the years of fear-inflicting policies were reinforced by Said’s revolt, it is now clear how the concepts of “Islam” and “Kurdish” could happily coexist. This was because being a Muslim and a Kurd would make a person a twofold criminal and guilty to the point of death in the eyes of the new regime. Even today, one can observe how some columnists, a la Committee of Union and Progress, grow uneasy when these two factors come together.