Islamic conquest of Persia ()

Synopsis:
Since the 1st century BC, the Romans and Parthians had waged a number of wars that lasted for the centuries. In fact these military campaigns outlasted the empires themselves. Both the Roman and Parthian Empires reformed and were replaced by the Byzantine and Sassanid Empires, respectively. These two new superpowers continued their territorial disputes and military confrontations for centuries. But the Sassanids and Byzantines also had various proxy wars, in which they attempted to start rebellions in the opponent's holdings. One example of this was the Byzantine client state the Ghassanids and the Sassanid client state the Lakhmids. These client states served as a buffer zone against the Southern Arab raiders. And both these client states were Arab in origin, but the Ghassanids were Christian Arabs whereas the Lakhmids aimed to unite all the Arabs under one kingdom. In fact the last independent ruler of the Lakhmids, Imru' al-Qais, claimed the title of "King of all the Arabs." This vision of Arab unity would not be realized for centuries, until the rise of Islam and the consolidation of the Rashidun Caliphate, in 632. Once the caliphate was established the Lakhmids were quick to join their Arab brethren. But this made the Sassanids very anxious, as they had lost their buffer zone and client state. And so the Sassanid rulers decided to stir up rebellions in the region. These provocations lead to the declaration of a Jihad against the Sassanid Persian Empire by Caliph Umar. At the time this seemed like an ant declaring war against a lion. That is how the Persians mistakenly perceived it.

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