During the Arab invasion of Iran, the Sasanian king Yazdegerd III (r. 632–651) sent 300 men under Siyah al-Uswari to defend Khuzestan.
[1] However, during the siege of Shushtar (641-642), Siyah and his men defected to the Arabs.
However, according to the Khuzestan Chronicle, Siyah and his men first defected to the Arabs after they entered Shushtar.
Furthermore, they also converted to Islam and allied themselves with the Banu Tamim of southern Iraq.
[3] However, the story about them converting to Islam is most likely inaccurate, since 15 years later, some members still appear with pure Zoroastrian Middle Persian names, such as a certain Mah Afridhan.