Yazdegerd kept urging the Persians at every opportunity, rebuking them for letting the Arabs seize their lands and even strike at them in their own fortresses. He therefore wrote to the people of Ahwaz and the rest of Persia, and they rose up, pledging and covenanting to wage war on the Muslims and to march against Basra.
When news of this reached ʿUmar, he wrote to Saʿd—who was then in Kufa—telling him to dispatch a large force to Ahwaz with al-Nuʿman ibn Muqarrin at its head, without delay, so that they might confront al-Hurmuzan. He also named a number of renowned and valiant commanders to serve in that army: Jarir ibn ʿAbd Allah al-Bajali, Jarir ibn ʿAbd Allah al-Himyari, al-Nuʿman ibn Muqarrin, Suwayd ibn Muqarrin, and ʿAbd Allah ibn Dhi’l-Sahmayn.
ʿUmar likewise wrote to Abu Musa—who was in Basra—instructing him to send a sizeable contingent to Ahwaz ⦗1⦘ and to place Suhayl ibn ʿAdiyy in command of it; with him were to be al-Barāʾ ibn Malik, ʿAsim ibn ʿAmr, Majzaʾah ibn Thawr, Kaʿb ibn Thawr, ʿArfajah ibn Harthamah, Hudhayfah ibn Mihsan, ʿAbd al-Rahman ibn Sahl, and al-Huṣayn ibn Maʿbad. Overall command of both the Kufan and Basran forces, and of whatever reinforcements might arrive, was to rest with Abu Sabrah ibn Abi Ruhm.
They relate that al-Nuʿman ibn Muqarrin set out with the Kufan army and reached Rām-Hurmuz ahead of the Basrans. Al-Hurmuzan was there; he came out with his troops, breaking the treaty he had concluded with the Muslims, hoping to defeat al-Nuʿman before the Basran forces could join him and so secure victory for the Persians. The two armies met at Irbil, where a fierce battle was fought. Al-Hurmuzan was routed and fled to Tustar, abandoning Rām-Hurmuz. Al-Nuʿman took the town by storm and seized its stores, treasures, weapons, and equipment.
When the Basrans heard what the Kufans had done to al-Hurmuzan and that he had taken refuge in Tustar, they headed for that city; the Kufans caught up with them and together they surrounded it, Abu Sabrah commanding the combined host. They found that al-Hurmuzan had gathered within its walls an immense and formidable force. The commanders wrote to ʿUmar describing the situation and asking for support, so he wrote to Abu Musa, ordering him to march to them. Abu Musa obeyed—he was the leader of the Basrans—while Abu Sabrah retained overall authority over both the Kufan and Basran contingents. They laid siege to the city for months ⦗2⦘, and heavy casualties were sustained on both sides.
On one of those days al-Barāʾ ibn Malik, the brother of Anas ibn Malik, slew a hundred warriors in single combat, apart from those he killed in the general fighting; Kaʿb ibn Sūr ⦗3⦘, Majzaʾah ibn Thawr, Abu Yamamah, and other Basrans did likewise. Among the Kufans as well, several men each killed a hundred challengers—such as Ḥabīb ibn Qurrah, Ribʿī ibn ʿĀmir, and ʿĀmir ibn ʿAbd al-Aswad ⦗4⦘. They fought in this manner for many days.
When the final assault was imminent, the Muslims said to al-Barāʾ ibn Malik—whose supplications were answered—“O Barāʾ, adjure your Lord to grant us victory.” He prayed, “O Allah, grant us victory and grant me martyrdom.” The Muslims then routed the enemy, driving them into their trenches and storming them. The idolaters withdrew into the city and fortified themselves there, the town now too cramped for them. A man from among the townsfolk sought safe-conduct from Abu Musa, and he granted it. The man then offered to show the Muslims a place from which they could enter the city—one of its approaches