Sassanian rule came to an end when the last Sassanian ruler, Yazdegerd III (632–651) was killed not far from the city and the Sassanian military governor surrendered to the approaching Arab army. The city was occupied by lieutenants of the caliph Umar and his successors where the conquest was including Tabaristan, Azerbaijan and Armenia. in later era it became the capital of the Umayyad province of Khorasan.