Shushtar was an ancient strong stronghold in Khuzestan, and was attacked by the Arabs under their commander Abu Musa Ashaari.

One year later, they invaded the rich Sasanian province Khuzestan, which was part of the domains of the Iranian aristocrat Hormuzan, who had, following the fall of Ctesiphon, retreated to Hormizd-Ardashir, which he used as his base in his raids in Meshan against the Arabs.

[1] The Sasanian king Yazdegerd III (r. 632–651) supported him in these raids and believed that it was possible to regain the territories that had been taken by the Arabs.

However, Hormuzan soon broke the peace by stopping paying tributes but was once again defeated, while the cities of Khuzestan were slowly subjugated one by one.

[4] According to al-Baladhuri, during the siege, the Arabs were reinforced with a group of professional Iranian elites under Siyah al-Uswari, known as the Asawira.

[7] By 651, most of Iran was under the control of the Arabs, and Yazdegerd III had been assassinated under the orders of his servant Mahoe Suri, an aristocrat from the Suren family, who served as the governor (marzban) of Merv, a powerful Sasanian stronghold.