Then ʿUmar reinforced Saʿd, after his departure, with one thousand men from Najd and two thousand Yemenis. Saʿd spent the winter at Zarūd. At that time al-Muthannā ibn Ḥārithah was in command of the Muslims over the lands Allah had opened in Iraq, but he succumbed to the wounds he had received on the Day of the Bridge of Abū ʿUbaydah. Before he died he appointed Bashīr ibn al-Khaṣāṣiyah to succeed him. Saʿd was still at Zarūd when this occurred, while Bashīr was accompanied by the delegations of the Iraqis. Saʿd then proceeded toward Iraq, and al-Ashʿath ibn Qays arrived to join him with 1,700 Yemenis.

The Battle of the Bridge:

In 13 AH ʿUmar had sent out an army under the command of Abū ʿUbayd al-Thaqafī. That same year—though some place it at the beginning of 14 AH—he met Jābān between al-Ḥīrah and al-Qādisiyyah. Allah routed the Magians: Jābān was captured and Mardānshāh was killed. Jābān later ransomed himself for two slave-boys, and Abū ʿUbayd did not realize he had taken the chief commander.

Abū ʿUbayd moved on to Kaskar, defeated Narsī, then confronted and defeated Jālīnūs. In response, Chosroes sent Dhū al-Ḥājib with 12,000 troops, heavy arms, and the White Elephant. When Abū ʿUbayd learned of their advance he crossed the Euphrates toward them and cut the bridge behind him. Dhū al-Ḥājib encamped at Qas al-Nāṭif, the river separating the two forces. He sent word: “Either you cross to us or we will cross to you.” Abū ʿUbayd answered, “We shall cross to you.” Ibn Ṣulūbā rebuilt the bridge; Abū ʿUbayd crossed, and the armies met in a narrow strip of land in Shawwāl. Dhū al-Ḥājib placed Jālīnūs in the van, accompanied by the elephant, and a fierce battle ensued. Abū ʿUbayd struck the elephant on its trunk, while Abū Mihjan severed its hamstring.