As part of the early Muslim conquests, which began under Muhammad in 622, the Rashidun Caliphate conquered the Sasanian Empire between 632 and 654. This event led to the decline of Zoroastrianism, which had been the official religion of Persia (or Iran) since the time of the Achaemenid Empire, circa 550 BC. 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 taken as refugees by various kings.
While Arabia was witnessing the rise of Islam in the 7th century, Persia was struggling with unprecedented political, economic and social issues as well as military weakness; the Sasanian army had greatly exhausted itself in the Byzantine–Sasanian War of 602–628. Following the execution of Sasanian shah Khosrow II in 628, Persia's internal political stability began to deteriorate rapidly, leading to ten new royal claimants being enthroned within the next four years. Shortly afterwards, Persia was further devastated by the Sasanian Interregnum, a large-scale civil war that began in 628 and resulted in the government's decentralization by 632.
