Muthanna returned from Madina to Hira in September 634 A D.
The Persians commissioned two forces to fight against the Muslims. One was placed under the command of Narsi and it was stationed at Kaskar. The other army under the command of Jaban was required to march to Hira. Heralds were sent to various parts of Iraq to foment an insurrection against the Muslims by appealing to their sense of religious honour.
Seeing the Persians to be in an offensive mood, Muthanna decided to remain on the defensive. All Muslim outposts in Suwad were pulled back and all Muslim garrisons were withdrawn to the west of the Euphrates. As Jaban marched through Suwad he met no resistance from the Muslims. As Jaban approached Hira, Muthanna evacuated Hira and moved to Khaftan closer to the desert. The strategy was to tempt the Persians come as near the desert as possible.
Abu Ubaid set off from Madina in September 634 with a force of one thousand fighting men. In the way he recruited more fighting men from the tribes, and when he reached Khaftan early in October he had a force of 4,000 fighting men with him.
Jaban crossed the Euphrates and camped at Namaraq near the site of modern day Kufa. Abu Ubaid moved with the Muslim forces from Khaftan, and came to Namaraq. At Namaraq the two armies were deployed for battle. The Persians led the attack, but the Muslim ranks held fast. Then the Muslims led the charge, and the Persians had to fall back. The Muslims redoubled the charge, and the Persians retreated confusion. The battle ended in the defeat of the Persians, who lost heavily. Jaban himself was captured by a Muslim soldier. Jaban did not reveal his identity and he bargained with his captor that if he was released he would offer two Persians in his place. The unsophisticated Muslim warrior agreed to the bargain, and Jaban was set free.
Later it was found that Jaban was the commander of the Persian forces and that he had escaped due to a stratagem. The matter was reported to Abu Ubaid. Abu Ubaid felt satisfied that a Muslim soldier had in fact given the promise to Jaban, and the Muslims could not go back on that promise.
This episode has been versified by Allama Iqbal in his poem.
"The Mysteries of Selflessness" as an illustration of Muslim brotherhood.
The poem reads:
"A certain general of Kind Yazdjird
Became a Muslim's captive in the wars;
A fireworshipper he was, inured to every trick
Of fortune, crafty, cunning, full of guile.
He kept his captor ignorant of his rank
Nor told him who he was, or what his name,
But said, "I beg that you will spare my life
And grant to me the quarter Muslims gain."
The Muslim sheathed his sword. "To shed thy blood,"
He cried "is forbidden for me."
When Kaveh's banner had been rent to shreds,
The fire of Satan's sons turned all to dust"
It was disclosed the captive was Jaban
The Commander of the Persian host.
Then was his fraud reported,
And his blood petitioned from the Arab General.
But Abu Ubaid the Muslim Commander
Answered their request
"Friends, we are Muslims, strings upon one lute
And of one concord.
Ali's voice attunes with Abu Dharr's,
Although the throat be that of Qanbar or Bilal.
Each one of us is trustee to the whole community
And one with it in malice or in truce.
As the Community is the sure base
On which the individual rests secure,
So is its covenant his sacred bond.
Though Jaban was a foeman to Islam,
A Muslim granted him immunity;
His blood, O followers of the best of men
Cannot be spilled by any Muslim sword."