When the Muslims occupied Ctesiphon the capital of Persia it did not mean that Persia had completely abandoned Iraq. In the north-east of Ctesiphon, the Persian forces gathered in great strength at Jalaula. Still further upstream the Tigris there was a concentration of the Persian forces at Takreet and Mosul.
When the Persian forces gathered at Jalaula, the Persian Governor of Mosul, Intaq by name collected some Persian forces and marched with them from Mosul to Takreet. He also collected large contingents from the Christian Arab tribes of Iyad, Taghlib and Namr. At Takreet he had a sizable Persian army. He dug a ditch round the city.
Takreet lay north-west of Jalaula, and the strategy was that the contingents from Takreet could be sent to the help of the Persian army at Jalaula. It was also believed that in the event of Persian defeat at Jalaula, the Persians could take a stand at Takreet.
Sa'ad b. Abi Waqqas reported this situation to Umar. Umar issued the following instructicns to Sa'ad b. Abi Waqqas:
"Send Abdullah b. Mut'am to deal with Intaq. The Commander of his advance guard will be Ribi b. Al-Afkal, of his right wing Haris b. Hassaan, of his left wing Furat b. Hayan, of his rear-guard Hani b. Qais, and of his cavalry Arafja bin Harsama."
Umar further instructed:
"If Allah defeats the two armies, the army of Mihran and the army of Intaq, send Qaqa b. Amr forward so that he is between the Suwad and the hills, on the boundaries of the Suwad, to act as the guard of the Muslims. May Allah preserve the Suwad for you."
Some time in May 637 A.D., Abdullah b. Mut'am marched from Ctesiphon with a force of 5,000 men, and arriving at Takreet invested the city Abdullah made several attempts to break the defences but the Persians held the ground.
With the Persians inside the city of Takreet there was a considerable strength of the Christian Arabs. Abdullah sent his agents to contact the Arab tribes in the city, and tried to persuade them not to support the Persians. He suggested that they should join the Muslim Arabs against the Persians. These overtures were successful and the Christian Arabs became lukewarm in their support of the Persians. The Persians soon noticed that the Arab tribe, were not active in the war effort and avoided war. Thereupon the Persians decided to evacuate secretly.
These developments were reported to Abdullah by the agents of the Christian tribes. The Christian Arab tribes offered to join the Muslims in case suitable terms were offered to them. Abdullah said that if the Christian tribes were sincere they should declare that there was no God but Allah and that Muhammad was the Messenger of God. The agents carried this message to their tribes inside the city. These agents returned after some time to tell Abdullah that the Christian Arabs agreed to accept Islam.
Abdullah decided that the main Muslim army would start the attack from the east across the ditch and would announce it with 'Takbeer'. Tha Arabian tribes within the city were required that as soon as they heard the Takbeer, they should raise the Takbeer and secure the western side of the city on the river front.
At night the Persian soldiers made preparations to embarked in the boats. At that time they heard the call of Allah-o-Akbar. The Persians were frightened and they thought that the Muslims had landed on the west edge of the city and cut their line of retreat. The Persians accordingly rushed eastward to escape from that side. Here they ran into the Muslim army which struck them with violence. The Persians pulled back and in the rear they were attacked by the Christian Arabs who had been converted to Islam. The Persians found themselves entrapped and they were killed in large numbers.
With the annihilation of the Persian army the Muslims occupied Takreet. As all the residents had accepted Islam there was great rejoicing at the occupation of the city by the Muslims.
Two days later, Abdullah sent a strong detachment of the army under Rabi bin Al-Akfal to Mosul. When the Muslims reached Mosul, the Persian garrison came out to fight. The Persians could not stand the Muslim attack and the Persians chose to surrender on the payment of Jizya in return for the safety of their lives and property.
Thereafter Abdullah also moved from Takreet to Mosul, and made arrangements for the administration of the area. After things had settled down Abdullah returned to Ctesiphon and left a garrison at Mosul under the command of Muslim bin Abdullah.
With the victories of Jalaula, Takreet, and Mosul, the Muslim hold on northern Suwad became firm.