Investigating the causes of Sunni weaknessIn Khorasan from the fifth to the middle of the seventh century AH

Sunni was the official and majority religion in Khorasan for six centuries. From the fifth century to the middle of the seventh, some factors weakened this religion. Identification and analysis of these factors is the subject of this article, which has been dealt with using historical, religious, rijal and class sources, literary and geographical books. The most important challenge for the Sunnis was the growth and spread of Shiism, which is a separate and independent category for discussion and research, and they will be dealt with the other causes in this article. Some external and internal factors have been effective in challenging and weakening the Sunnis. These factors mostly occurred in the second half of the fifth, sixth and seventh centuries. Sectarianism, Sunni conflicts with Shiism, and the emigration of ulema are internal factors, and external factors such as dependence on governments, the Ghazan invasion, and the Mongol invasion. Of course, the Mongol invasion accelerated the decline of the Sunnis in Khorasan.