However, all of Iran was still not under Arab control, and the region of
Daylam was under the control of the
Daylamites, while
Tabaristan was under
Dabuyid and
Paduspanid control, and the
Mount Damavand region under
Masmughans of Damavand. The Arabs had invaded these regions several times but achieved no decisive result because of the inaccessible terrain of the regions. The most prominent ruler of the Dabuyids, known as
Farrukhan the Great (712–728), managed to hold his domains during his long struggle against the Arab general
Yazid ibn al-Muhallab, who was defeated by a combined Daylamite–Dabuyid army, and was forced to retreat from Tabaristan.