Since at least the mid-fifteenth century, the Safavid order, which was established by Shaykh Ṣafī al-Dīn of Ardabil (d. 1334) as an ostensibly Sufi tariqah (Sufi order), had become increasingly important as a political force in the territories of the Aqquyunlu in Iraq, Anatolia, and Azerbaijan. It was during the period when Shaykh Junayd ibn Ibrahīm (d. 1460) assumed leadership of the Safavid order that it became explicitly Shi’ite and closely affiliated with the more ghulati (extremist/heterodox) strands of Shi‘ism.

Between 1501 and 1510 the first Safavid king Isma’il utilized his spiritual authority (to mobilize his Kizilbash followers to conquer all the regions between eastern Anatolia and Khurasan. He successfully overthrew the remnants of the Aqquyunlu dynasty and set out to conquer a large swathe of territory, seizing the Shirvanid capital of Baku (1500), Tabriz (1501), Isfahan (1503), as well as the old Abbasid capital of Baghdad (1508), and established his sovereignty over Persia, Azerbaijan, Eastern Anatolia, and Iraq, effectively unifying the old territories of Iran for the first time in centuries. In 1510, he defeated and killed the Uzbek ruler Shaybani Khan (d. 1510) and extended his rule into Khurasan and brought both Mashhad and Herat under his control. Following his conquests, he established Twelver Shi’ism as the state religion throughout his domains, and violently imposed this creed upon his (largely Sunni) subjects in Iran, Iraq, and Azerbaijan by introducing the Shi’i call to prayer and instituting the practice of sabb whereby the first three Caliphs, the Prophet’s wife Ā’isha, and a number of the Prophet’s Companions were ritually cursed and vilified. This practice was particularly emphasized in regions where the majority of the population was Sunni, and most of the population was forced to engage in it or face persecution. There are examples of several prominent clerics being executed for their refusal to publicly participate in this practice.

Ismā‘īl’s conquests were accompanied by mass violence against Sunni communities, the devastation of their property, and the destruction of  shrines, including those of the important figures of Abu Ḥanifa (d. 767) and ‘Abd al-Qadir Gilani (d. 1166) in Baghdad.

Various massacres also took place:

10,000 were executed near Hamadan in 1503; 4000 members of the Kaziruni Sufi order were murdered in Fars, while all the tombs of rival Sufi orders were desecrated; ten thousand refuges and dissenters who took up refuge in Asta were put to the sword; the entire cities of Yazd, Tabas and Abarquh was slaughtered, tens of thousands of people in these three cities alone according to Safavid chronicles; in Khurasan, the tomb of Abd al-Rahman Jami (d. 1492) was destroyed and the entire population of Qarshi—about 15,000 people—massacred. The violent institutionalization of Shi‘ism and the brutal eradication of Sunni Islam in the lands under Safavid rule is what many Iranian nationalists and the Shia clergy  sell as the ‘gradual conversion to Shi’ism’, making it seem as if Iranians were naturally inclined to Shi’ism and happily accepted it at the hands of the Safavids.

The Sunni community of Iran, which had existed for centuries in the country, was permanently destroyed between the early sixteenth and late seventeenth centuries through a sustained process of mass violence, forced conversion, exile, the destruction of religious institutions, and a concentrated program of religious propaganda aimed at transforming the country into a bastion of Twelver Shi‘ism. By the late seventeenth century, the only Sunni communities that remained were those  residing along Iran’s frontiers and they were treated with varying degrees of toleration.

(Shah Isma’il imposing Shi’ism as the state religion of Iran at Tabriz in 1501. From the History of Shah Isma’il, British Library MS. Or 3248 [Ross Anonymous], fol. 74a)