In this battle, the Muslims took their revenge on the Iranians. When the Persian commanders heard that the number of soldiers in Musanna’s army had increased, they sent another army under the command of Mehran against Musanna. The Persian army and Musanna’s army met at a place called Buweib. Buweib is a town one day’s distance from Kufa, with the Euphrates River lying between Kufa and Buweib. The Persians said:
– Either you cross the river and come to us, or we will cross and come to you. The Muslims replied:
– No, you cross the river and come to us. Upon this, the Persians crossed the river and came to where the Muslims were. This event took place in the month of Ramadan. Commander Musanna ordered the Muslims to break their fasts. Thereupon, the whole army broke their fast. Thus, they were strengthened. Musanna arranged his soldiers. He went to each place where a banner was stationed and spoke with the commanders. He gave advice to the tribes and encouraged them to strive in jihad. He advised them to be patient and silent. Among the soldiers was Jarir b. ʿAbdullah al-Bajali, who was present with a group from his people. The leading Muslim personalities were also present in this army. Musanna said to them:
– I will say the takbir (Allāhu akbar) three times. Be prepared; when I say the takbir for the fourth time, launch the attack.
The Muslim soldiers listened to and obeyed his command. When Musanna made the first takbir, the Persians hurried and attacked the Muslims, almost rendering them unable to move. They fought fiercely. Musanna saw that breaches had formed in some of his ranks. He sent them the following message through a man:
– The commander sends you greetings and says: "Do not disgrace the Arabs today."
Upon receiving this message, the Banu Ijl tribe immediately straightened their ranks and began to close the gaps among them. When Musanna saw this, he was pleased and began to smile. Then he sent them another message:
– O Muslim community! However you used to deal with such people, do so now as well. Support the religion of Allah so that Allah may support you.
Musanna and the Muslims were making dua (supplication) to Allah to grant them victory and aid. As the battle dragged on, Musanna gathered a group of his brave companions and placed them behind him for protection, and he himself attacked Mehran directly. He forced him to retreat from his position. Finally, he entered the right wing of the army. A Christian slave from the Banu Taghlib tribe attacked Mehran, killed him, and mounted his horse.
According to Muhammad b. Ishaq, the person who attacked Mehran was Mundhir b. Hasan b. Dirar al-Dabbi. Mundhir threw his spear and struck Mehran, and Jarir b. ʿAbdullah al-Bajali cut off Mehran’s head. The two disputed over the spoils on Mehran; in the end, Jarir took his weapon, and Mundhir took his belt.
When the Magians (Majūsī) were routed and began to flee, the Muslims pursued and separated them from one another.
Musanna b. Haritha had sent guards to the bridgehead to prevent the Persians who came there from crossing the bridge, while allowing the Muslims to cross. For the rest of the day and night, the Muslims continued to chase them. It is reported that nearly 100,000 Magian soldiers perished that day—some were killed, others drowned in the water. Praise and gratitude be to Allah.
The Muslims seized abundant spoils. Some of these spoils were goods, others were foodstuffs. They sent the good news and one-fifth of the spoils to ʿUmar. Many of the leading Muslim personalities were martyred in this battle. Also, as a result of this battle, the Persians were humbled. The Companions (ṣaḥāba) gained the opportunity to attack the Persian lands between the Euphrates and Tigris. An uncountable amount of spoils was captured.
After the Battle of Buweib, several other events occurred that would take a long time to recount. This battle in Iraq corresponded to the Battle of Yarmuk that took place in Syria. Regarding this battle, ʿAwwar al-Shani al-ʿAbdi recited the following poem:
"The sorrows stirred against ʿAwwar, the home of the tribe.
And after ʿAbd al-Qays, they turned to Hassan at ʿAwwar.
While our order and stability were intact at Nahila,
They turned Mehran’s army into corpses.
At that moment, Musanna advanced upon them with his cavalry.
He killed the warriors among the Persians.
He destroyed Mehran and his accompanying soldiers.
Musanna and his soldiers destroyed them one by one."