After withdrawal from Ctesiphon, the Persian armies gathered at Jalaula north-east of Ctesiphon. Jalaula was situated in the neighbourhood of what is modern Baghdad. It lay on the main road to Khurasan. Jalaula was a place of strategical importance from where routes led to Iraq, Khurasan and Azerbaijan.
The Persian forces at Jalaula were commanded by General Mihran. His deputy was General Khurrazad a brother of General Rustam. The Persians made great preparations for a large scale battle against the Muslims. The entire town was converted into a fortress. A deep ditch was dug round the city. Various fortifications were constructed behind the ditch. In front of the ditch caltrops were strewn in large numbers with a view to laming the horses of the advancing enemy. The Persian troops took an oath by the sacred fire that they would die fighting rather than retreat. The town was stocked with provisions, and the Persians prepared themselves with grim determination for a long siege.
When Saad came to know of the preparations that the Persians had mad to defied Jalaula he reported the intelligence to Umar and asked for his orders. With the Persian army quartered at Jalaula the Muslim hold on Ctesiphon could never be firm. The Caliph, therefore, ordered that steps should be taken to capture Jalaula. He directed Sa'ad b. Abi Waqqas that Hashim b. Utbah should be sent on the expedition against lalaula at the head of a force of twelve thousand men. The Caliph further ordered that the vanguard should be commanded by Qaqa; the right wing by Musir b. Malik; the left wing by, Amr b. Malik; and the rear-guard by Amr b. Marrah.
Some time in April 637 A.D., Hashim marched at the head of 12,00O troops from Ctesiphon, and arriving at Jalaula found that the Persians were in a strong position with fortifications, entrenchments, deep ditch, and a belt of caltrops. Hashim established his camp and decided to lay a siege to Jalaula.
The siege dragged on for seven months. There were occasional skirmishes but these led no where. The Persians continued to get reinforcements from Hulwan. Some time in November heavily reinforced the Persians decided to launch an offensive and drive away the Muslims. This suited the Muslims. Hashim pulled back his army so that the entire Persian army might be brought in the field.
The action began with a heavy attack by the Persians all along the front. The Muslims withstood the ground but as the Persians intersified their pressure some Muslim units were pushed back, and they were exposed to the danger of a collapse. Hashim dashed forward to such units, and exhorted them to hold fast. He assured them that the battle of Jalaula was going to be the last battle and it had to be won at all costs. The fight continued with considerable violence. The battle was carried with arrows; then with javelins, spears and lances; and thereafter with swords and maces.
In the afternoon there was a short break in fighting. When the fighting was resumed,the Muslims launched the attack. Qaqa with his reserve made a flanking movement and reached the ditch in the rear of the Persian army. Late in the afternoon a storm began to blow. So severe was the dust storm that the land became dark. The storm blew in the faces of the Persians, and helped the Muslims rush forward with greater momentum. The fighting was savage and each side fought with fanatical fury. When the combat was going on violently, Qaqa raised the cry from behind the Persian forces, "O Muslims I am here. I have captured the ditch. Come to me."
At this call, the Muslim forces attacking the Persians from the front increased the violence of their attack. As the Persians moved back they had to face the attack from the rear by the men of Qaga. The storm also gained in virulence. In the face of these hostile circumstances the Persian resistance broke and they dispersed in all directions. The Muslims pursued them, and the Persians were slaughtered in large numbers. According to Tabari one laku Persians were killed in the battle of Jalaula. Even though this figure tnight be somewhat exaggerated, the Persian loss was colossal. Mibran found safety in flight to Hulwan.
The Muslims occupied Jalaula. As the Persian army had withdrawn, the residents surrendered on the usual terms of Jizya. The spoils of war collected were valued at 30 million dirhams. After setting aside the usual one-fifth state share, the rest was distributed among the warriors. The share of each warrior came to 9,000 dirhams.
The State share of the booty was sent to Madina through Ziyad. A public assembly was convence and the faithful gathered in the Prophet's mosque to hear an account of the Muslim victory at the battle of Jalaula. Ziyad gave such an eloquent and graphic description of the battle that Umar admiringly said, "This is what an orator should be." Ziyad said that the credit for such narration was due to the heroic, deeds performed by the warriors of Islam.
The property brought in booty was stored in the courtyard of the mosque and Abdur Rahman b. Auf and Ahdullah b. Arqam kept watch over the property during the night. In the morning under the supervision of Umar the mantle that covered the goods was drawn aside, and it was found that besides vast property and goods there were vast sums in gold and silver.
Umar ordered the immediate distribution of the property among the Muslims. As the property was distributed tears trickled from the eyes of Umar. The faithful gathered round Umar enquired as to the reason for his weeping Umar said, "God be praised for showering so much wealth on the Muslims. I weep because I am afraid that where riches appear, envy and jealousy are bound to follow in their wake."