Battle of Nahavand
The Battle of Nahavand ( , ), also spelled Nihavand or Nahawand, was fought in 642 between the Rashidun Muslim forces under caliph Umar and Sasanian Persian armies under King Yazdegerd III. Yazdegerd escaped to the Merv area, but was unable to raise another substantial army. It was a victory for the Rashidun Caliphate and the Persians consequently lost the surrounding cities including Spahan (Isfahan). The former Sassanid provinces, in alliance with Parthian and White Hun nobles, resisted for about a century in the region south of the Caspian Sea, even as the Rashidun Caliphate was replaced by the Umayyads, thus perpetuating the Sassanid court styles, Zoroastrian religion, and Persian language. Background At the time of the death of the Islamic Prophet Muhammad in 632, the religion that he led dominated the Hejaz (western Arabia). Under the first two caliphs Abu Bakr and Umar, Islam expanded into Palestine and Mesopotamia where it respectively confronted the East Roman and Persian (Sāsānian) empires. Both were exhausted by warfare and internal dissent. With the East Roman defeat at the Battle of Yarmouk (636), the Muslim Arabs were free to turn east to the Euphrates and the Persian heartland. In November 636 a Sāsānian