Spāhbad is a Middle Persian title meaning "army chief" used chiefly in the Sasanian Empire. Originally there was a single spāhbad, called the Ērān-spāhbed, who functioned as the generalissimo of the Sasanian army. From the time of Khosrow I on, the office was split in four, with a spāhbad for each of the cardinal directions. After the Muslim conquest of Persia, the spāhbed of the East managed to retain his authority over the inaccessible mountainous region of Tabaristan on the southern shore of the Caspian Sea, where the title, often in its Islamic form ispahbedh, survived as a regnal title until the Mongol conquests of the 13th century. An equivalent title of Persian origin, ispahsālār or sipahsālār, gained great currency across the Muslim world in the 10th–15th centuries.

The Muslim conquest of Persia, also called the Muslim conquest of Iran, the Arab conquest of Persia, or the Arab conquest of Iran, was a major military campaign undertaken by the Rashidun Caliphate between 632 and 654. As part of the early Muslim conquests, which had begun under Muhammad in 622, it led to the fall of the Sasanian Empire and the eventual decline of Zoroastrianism, which had been predominant throughout Persia as the nation's official religion. The persecution of Zoroastrians by the early Muslims during and after this conflict prompted many of them to flee eastward to India, where they were granted refuge by various kings.