The Lakhmid dynasty was a pre-Islamic Arab state centered around the borderlands between Mesopotamia and the deserts of Arabia and the urban center of Al-Hirah. They were crucial in repelling the raids of Bedouin tribesmen, and served as a valuable buffer state, especially against the Byzantine-backed Ghassanids. However, Khosrau II imprisoned the Lakhmid ruler, Al-Numan-III, and this led to a chain of events that led to them being dissolved and the battle of Dhi Qar. What if Khosrau had not done so, and the Sassanids leave the Lakhmids alone until the Arab conquest? Could Al-Hirah become a prominent administrative and economic center under the Caliphate? How would this affect the conquest of the Sassanids? How does this affect the First Fitna, but I think I'm going too far into things at that point.