The Arab conquest of Iran

Drained by decades of war with Byzantium and by palace coups, the Sasanian state cannot withstand the Arab onslaught. The defeat at Qadisiyya opens Mesopotamia to the Muslims, the battle of Nahavand decides the fate of the plateau, and the last king, Yazdegerd III, flees east and perishes in 651. Zoroastrianism slowly gives way to Islam; some communities leave for India and become the Parsis there — but the Persian language and court culture survive and do much to shape the coming caliphate. The Jewish communities of Mesopotamia pass under the new power with their academies intact.