Yazid-ibn-Mohalleb, a general under the Umayyads, was appointed the head of a great army to lead the Mazandaran expedition. On the way to Mazandaran, the general ordered captives to be hanged at the two sides of the road so that the victorious Arab army pass through. The attack on Tabarestan (present-day Mazandaran) failed, but he established his control in Gorgan. By the orders of Yazid-ibn-Mohalleb so many Persians were beheaded in Gorgan that their blood mixed with water would energize the millstone to produce as much as one day meal for him, as he had vowed. The extent of his brutality represented itself by running watermills by people's blood for three days and he fed his army with the bread made from that very bloody flour. But, Tabarestan remained invincible until the majority of Zoroastrians migrated towards India and the rest converted to Islam gradually.