Islam is by far the most practiced religion in Turkey. Most Turkish people are Sunni Muslims, and most of them belong to the Hanafi school of jurisprudence. Smaller numbers belong to the Alevi, Ja'fari and Alawite minorities. The established presence of Islam in the region that now constitutes modern Turkey dates back to the second half of the 11th century, when the Seljuks started expanding into eastern Anatolia.
While official records indicate the population of Turkey to be 99.8% Muslim, most surveys estimate the percentage to be around 90 to 95%. Because the government registers everyone as Muslim at birth by default, the official statistics can be misleading.
The Hanafi school of fiqh (maddhab) of Sunni Islam makes up about 90% of the Muslim population, with the remaining Muslim sects consisting of Alevis (close to 10%), Ja'faris (representing 1%) and Alawites (with an estimated population of around 500,000 to 1 million, or about 1%). With a sizeable part of population being Cultural Muslims, there is also a minority of Sufi and non-denominational Muslims.
Whether "Turkish Islam" is more "moderate and pluralistic" compared to other Islamic societies is disputed, with a majority claiming this to be true. Reasons given for this statement include: the state constitution not containing any references to Islam, alcohol consumption being prevalent, and instead of promoting religious activities there was a state-imposed ban on Islamic attire and restrictions on religious activities until the late 2010s. Others argue this view is not valid, pointing to the fact that many elements of Turkish society are hardliners.Erturk, Omer F. "The myth of Turkish Islam: the influence of Naqshbandi-Gümüşhanevi thought in Turkish Islamic orthodoxy." British Journal of Middle Eastern Studies 49.2 (2022): 223-247.
History
Seljuks and initial history
During the Muslim conquests of the 7th and early 8th centuries, Arab armies established the Islamic Empire. The Umayyad Caliphate continued the spread of Islam. The Islamic Golden Age was soon inaugurated by the middle of the 8th century by the ascension of the Abbasid Caliphate and the transfer of the capital from Damascus to Baghdad.Gregorian, Vartan. Islam: A Mosaic, Not a Monolith, Brookings Institution Press, 2003, pp. 26–38
The later period saw initial expansion and the capture of Crete (840). The Abbasids soon shifted their attention towards the East. During the later fragmentation of the Abbasid rule and the rise of their Shiite rivals the Fatimids and Buyids, a resurgent Byzantium recaptured Crete and Cilicia in 961, Cyprus in 965, and pushed into the Levant by 975. The Byzantines successfully contested with the Fatimids for influence in the region until the arrival of the Seljuk Turks who first allied with the Abbasids and then ruled as the de facto rulers.
In 1068, Alp Arslan and allied Turkoman tribes recaptured many Abbasid lands and even invaded Byzantine regions, pushing further into eastern and central Anatolia after a major victory at the Battle of Manzikert in 1071. The disintegration of the Seljuk dynasty resulted in the rise of subsequent, smaller, rival Turkic kingdoms such as the Danishmends, the Sultanate of Rum, and various Atabegs who contested the control of the region during the Crusades and incrementally expanded across Anatolia until the rise of the Ottoman Empire.
Ottoman Empire
Beginning in the 12th century, new waves of Turkic migrants arrived, many of whom belonging to Sufi orders. Some of these migrants later went on to incorporate heterodox beliefs. One Sufi order that appealed to Turks in Anatolia was the Safaviyya, an order that was originally Sunni and non-political, but later became both Shi'a and politically based in northwest Iran. During the 14th and 15th centuries, the Safavid and similar orders such as the Bektaşi became rivals of the Ottomans—who were orthodox Sunni Muslims—for political control of eastern Anatolia. Although the Bektaşi order became accepted as a sect of orthodox Sunni Muslims, they did not abandon their heterodox beliefs. In contrast, the Safavids eventually conquered Iran, spread their beliefs, and became proponents of orthodox Twelver Shi'a Islam.
The conquest of the Byzantine capital of Constantinople (modern day Istanbul) in 1453 enabled the Ottomans to consolidate their empire in Anatolia and Thrace. The Ottomans later revived the title of caliph during the reign of Selim I. Despite the absence of a formal institutional structure, Sunni religious functionaries continued to play an important political role. In theory, the codified system of sharia regulated all aspects of everyday life, at least for Muslim subjects of the empire. The head of the judiciary ranked directly below the sultan, and was second in power only to the grand vizier. Early in the Ottoman period, the office of grand mufti of Istanbul evolved into that of Şeyhülislam (shaykh, or "leader of Islam"), which had ultimate jurisdiction over all the courts in the empire and consequently exercised authority over the interpretation and application of sharia. Legal opinions pronounced by the Şeyhülislam were considered definitive interpretations.
Republic of Turkey
One-party period
The secularization of Turkey started during the last years of the Ottoman Empire and was a prominent feature of Atatürk's reforms. Secularism (or laiklik) became one of the "Six Arrows" of Atatürk's program for remaking Turkey. Under his leadership, in 1922, the caliphate was abolished, and the secular power of religious authorities and functionaries was reduced and eventually eliminated. Religious foundations were nationalized. The influential and popular orders of the dervish brotherhoods (Tariqa) were also suppressed.
In 1922, the new nationalist regime abolished the Ottoman sultanate, as well as the caliphate in 1924 - the religious office that Ottoman sultans had held for four centuries. Thus, for the first time in Islamic history, no ruler claimed spiritual leadership of Islam.
Atatürk and his associates abolished certain religious practices and institutions and generally questioned the value of religion, preferring to place their trust in science. They regarded organized religion as an anachronism and contrasted it unfavorably with "civilization", which to them meant a rationalist, secular culture. Unlike in the West, the establishment of secularism in Turkey was not a gradual process of separation of mosque and state.
In the Ottoman Empire, all residents, at least theoretically, had been subject to traditional religious law, and Sunni religious organizations had been part of the state structure. However, the state usually had authority over the clergy and religious law (e.g. many Sultans are known to change Şeyhülislams, who do not approve of state politics). When the reformers of the early 1920s opted for a secular state, they removed religion from the sphere of public policy and restricted it to exclusively that of personal morals, behavior, and faith. Although private observance of religious rituals could continue, religion and religious organization were excluded from public life.
In addition to the abolition of the caliphate, new laws mandated the abolition of the office of Şeyhülislam and the religious hierarchy, the closing and confiscation of Sufi lodges, meeting places, and monasteries and the outlawing of their rituals and meetings, the establishment of government control over vakıfs which had been inalienable under Sharia, the replacement of sharia with adapted European legal codes; the closing of religious schools; the abandonment of the Islamic calendar in favor of the Gregorian calendar used in the West, and restrictions on public attire that had religious associations, with the fez outlawed for men and the veil discouraged for women.
Atatürk and his colleagues also attempted to "turkify" Islam through official encouragement of practices such as the usage of Turkish rather than Arabic at devotions, substituting the Turkish word Tanrı for the Arabic word Allah, and incorporating Turkish into daily calls to prayer. These changes in devotional practices caused widespread criticism among Muslims, which led to a return to the Arabic version of the call to prayer in 1950, after the opposition party DP won the elections. Of longer-lasting effect were the regime's measures of prohibiting religious education, restricting the building of new mosques, and transferring existing mosques to secular purposes - most notably the Hagia Sophia (Justinian's sixth-century Christian basilica, which had been converted into a mosque by Mehmet II), which was turned into a museum in 1935. Muftis and imams were appointed by the government, and religious instruction was taken over by the Ministry of National Education. As a result of these policies, the Turkish Republic was judged negatively by some sections of the Muslim world.
The common expectation was that these policies of the 1920s and 1930s would diminish the role of religion in public, which, however, did not occur. As early as 1925, religious grievances were one of the principal causes of the Şeyh Sait rebellion, an uprising in southeastern Turkey that may have claimed as many as 30,000 lives before being suppressed.
Although Turkey was secularized at a legal level, religion remained a strong force. After 1950, some political leaders espoused support for programs and policies that appealed to the religiously inclined in an attempt to benefit from a lot of the population's attachment to religion. Such efforts were opposed by most of the state, who believed that secularism was an essential principle of Kemalist Ideology. This gradually led to a polarization of the entire country, which became especially evident in the 1980s, as a new generation of religiously motivated local leaders emerged to challenge the dominance of the secularized political elite.
Multi-party period
Following the loosening of authoritarian political control in 1946, a large number of people began to openly call for a return to traditional religious practices. During the 1950s, even certain political leaders found it expedient to join religious leaders in advocating more state respect for religion.
A more direct manifestation of the growing reaction against secularism was the revival of the Sufi brotherhoods. Not only did suppressed Sufi orders such as the Kadiri, Mevlevi, Nakşibendi, Khālidiyyā and Al-Ṭarīqah al-Tijāniyyah reemerge, but new movements were formed, including the Nur Cemaati, Gülen movement, Sülaymānīyyā, Community of İskenderpaşa and İsmailağa. The Tijāni became especially militant in confronting the state, damaging monuments to Atatürk to symbolize their opposition to his policy of secularization. This was, however, an isolated incident and only involved one particular Sheikh of the order. Throughout the 1950s, there were numerous trials of Ticani and other Sufi leaders for anti-state activities.
Simultaneously, some movements, notably the Süleymancı and Nurcular, cooperated with those politicians perceived as supportive of pro-Islamic policies. The Nurcular eventually advocated support for Turkey's multi-party political system, and one of its offshoots, the Gülen movement, had supported the True Path Party while the Işıkçılar and Enver Ören had openly supported the Motherland Party since the mid-1980s.
The demand for restoration of religious education in public schools began in the late 1940s. The government initially responded by authorizing religious instruction in state schools for those students whose parents requested it. Under the rule of the Democrat Party during the 1950s, religious education was made compulsory in secondary schools unless parents made a specific request to have their children excused. Religious education was made compulsory for all primary and secondary school children in 1982.