The Sassanids
- 224 to 621 CE, The area was subject to Sassanid dynasty. The area is known as Xuzestan during this period.
During the early years of the reign of Shapur II (309-379), Arabs crossed the Persian Gulf from Bahrain to "Ardashir-Khora" of Fars and raided the interior. In retaliation, Shapur II led an expedition through Bahrain, defeated the combined forces of the Arab tribes of Taghleb, Bakr bin Wael, and Abd Al-Qays and advanced temporarily into Yamama in central Najd. The Sassanids resettled these tribes in Kerman and Ahvaz. Arabs named Shapur II, as Shabur Dhul-aktāf (he who owns shoulders because either he pierced or dislocated captured Arabs shoulders or he had wide shoulders) after this battle. (p. 202, Encyclopædia Iranica).
It should be pointed out that the Arab presence in Iran, did not begin with the Arab conquest of the Sassanid Empire. Mutual infiltration into and out of Iran, began before the Muslim conquests and continued as a result of joint exertions of the civilized Arabs (ahl al-madar) as well as the desert Arabs (ahl al-wabar). There were tribesmen of Bakr bin Wael and Tamim(Thamim) in Khuzestan and Fars prior to the arrival of the Arab Muslim Armies. Some of these Arab groups were sedentary while others were nomadic. Some fought on behalf of the Sassanid Empire (Taghleb, Eyad), while others (Lakhmid, Shayban, Bakr bin Wael) began struggling against the Sassanids. These latter group had already won a celebrated, if limited, victory at Du Qar around 604 CE
Some local Arabs led by Al-Motanna bin Hareta Al-Shaybani helped to direct the attention of the nascent Muslim state toward Iran by converting to Islam and negotiating with Medina for support in their anti-Sassanid moves. (p. 210-211 Encyclopædia Iranica ).
Read more about this topic: History Of Khuzestan Province