In the ninth to fourteenth centuries, the northern Iranian regions of Tabaristan, Daylam and Gilan, sandwiched between the Caspian Sea and the Alborz range, come under the rule of a number of Alid dynasties, espousing the Zaydi branch of Shi'ism.

The first and most powerful Zaydi emirate is established in Tabaristan in 864 and lasts until 928.

It is interrupted by Samanid occupation in 900, but restored in 914 by another Alid branch.

The second period of the Alid emirate is plagued by internal dissensions and power struggles between the two branches, and ends in the second conquest of the region by the Samanids in 928.

Subsequently, some of the soldiers and generals of the Alavids join the Samanids, among them the founder of the Ziyarid dynasty, Mardavij, and Ali, Hassan and Ahmad, the sons of Buya and founders of the Buyid dynasty.Local Zaydi rulers survive in Daylam and Gilan until the 16th century.