A Study on the Reasons of Sasanian Decline and Fall According to the First Islamic Centuries, Historian Sources

Sassanid reign, as one of the most powerful Iranian dynasties, lasted for over four centuries before the Arab Moslems’ attack to Iran. The great Sassanid government managed to convert the Feudal Iran of Parthian era into a united and strong country thanks to its central government and Zoroastrianism nationalism; this not only recreated political power but also hugely revolutionized the cultural and social issues in Iran. However, different factors, after a while, led to the gradual weakness and suppression of this dynasty before the Arab Moslems’ attack. In this research, auditing the historians of all these four centuries of the early Islamic era including Abou- HanifehDinvari, Yaghoubi, Masoudi, Tabari, and EbneMoskouyeh exactly and from all aspects, many attempts have been made to figure out and analyze the reasons of this gradual weakness and overthrown of Sassanid Reign the emnloying a historical-descriptive method. The results of this research reveal that in the view of the historians of all these four centuries of the early Islamic era, the following factors were the most crucial reasons of Sassanid’s downfall and defeat before the Arab Moslems: religious prejudice, high position of Zoroastrian clergymen, well-borns’ increasing power, massacre of the royal family by Shirouyeh, the last Sassanid kings’ lack of authority, a military coup against the kings, long exhausting overseas battles, especially the constant wars against the Rome Empires, toppling the Ale-Lakhm by KhosrouParviz, economic pressures on people and heavy taxes, natural disasters like the Tigris and Euphrates rivers bursting their banks, and hidden helps.