Muslim Conquest of Persia

The Muslim conquest of Persia led to the end of the Sassanid Empire in 644, of the Sassanid dynasty in 651 and the eventual extirpation of the Zoroastrian religion in Persia. The Sassanid Empire was first invaded by Muslims in present day Iraq in 633 under general Khalid ibn Walid, which resulted in Muslim conquest of Iraq. Following the transfer of Khalid to the Roman front in the Levant, Muslims eventually lost Iraq to Persian counter attacks. The second invasion of Iraq began in 636 under Saad ibn Abi Waqqas when after a key victory at the Battle of Qadisiyyah Sassanid control west of Persia was permanently ended. The Zagros mountains became a natural barrier and borders between the Rashidun Caliphate and the Sassanid empire. Owing to continuous raids by Persians in Iraq, Caliph Umar ordered a wholesale invasion of the Sassanid Persian empire in 642 which came to an end with complete conquest of the Sassanids by mid 644.