After an Arab incursion into Sasanian territories, the energetic shah (king) Yazdgerd III, who had just ascended the Persian throne, raised an army to resist the conquerors. Many of the marzbans refused to come out to help the shahinshah. However, the Persians suffered a devastating defeat at the Battle of al-Qadisiyyah in 636. Little is known about the Battle of al-Qadisiyyah other than it lasted for several days by the banks of the river Euphrates in what is now Iraq and ended with the Persian force being annihilated. Abolishing the Lakhmid Arab buffer state had forced the Persians to take over the desert defense themselves, leaving them overextended.
