Seljuq Empire
Sunni Muslims are the second-largest religious group in Iran. Specifically, Sunni Muslims came to power in Iran after the period when Sunni were distinguished from Shi'a by the Ghaznavids who ruled Iran from 975–1186 AD, followed by the rule of the Great Seljuq Empire and the Khwarazm-Shah dynasty which ruled Iran until the Mongol invasion of Iran. Sunni Muslims returned to power when Ghazan converted to Sunni Islam.