In the second week of January 637, Zuhra advanced with his corps and reached Sabat four miles from Ctesiphon. It was a Persian cantonment, but there was no garrison there. The Mayor of Sabat, Sheerzad waited on Zuhra and offered allegiance to the Muslims. The residents were given protection on the usual terms. Now the entire land upto the very gates of Ctesiphon belonged to the Muslims.
Ctesiphon the capital of Persia was not one city; it was a conglomeration of several cities. Indeed the Arabs called Ctesiphon 'Al-Madain', meaning the cities. The main city I lay on the eastern bank of the Tigris. One of the cities forming part of 'Al-Madain' lay on the western bank of the Tigris and was known as Bahrseer.
Bahrseer had been prepared for defence, and a deep ditch had been dug round the perimeter of the suburb. As the Muslim advance guard approached Bahrseer, the Persian garrison within the fortified city hurled stones at the Muslims through ballistas and catapults. The Muslims pulled back beyond the range of the stones and decided to lay siege to the city.
The siege began in January 637, and dragged on for two months. The supplies from the countryside on which Bahrseer depended were entirely cut off, and the citizens were reduced to eating cats and dogs. Things for the Persian force became still worse, when some of the Persians who had accepted the Muslim rule, built for the Muslims engines which could throw stones. Equipped with these engines, the Muslims were able to answer the Persian military fire, stone for stone. That caused considerable havoc among the besieged citizens.
One day in March 637, cut to sore straits, the Persian garrison called forth from the city in the determined effort to break through the Muslim ranks. The Persian forces were led by a fierce lion which had been specially trained for war. The lion rushed at the Muslim front, and the Muslim horses bolted causing considerable harms. Hashim who was commanding the vanguard of the Muslim forces rushed at the lion with his sword and dealt it such a well directed blow that it fell dead. Saad the Commander-in-Chief of the Muslim forces stepped forward to kiss Hashim bin Utba on the forehead as a mark of admiration for his act of unparalleled heroism.
The Commander of the Persian force gave a challenge for a personal duel. The challenge vies accepted by Zuhra bin Al-Hawiyya. In the exciting duel that followed, Zuhra killed the Persian Commander. Then the two armies clashed, and the fight continued till the night set. In the battle an arrow struck Zuhra, the hero of the march to Ctesiphon, and the great hero died. He was buried with full military honours.
After the break in fighting, a Persian emissary came to the Muslim camp to convey a message from the Persian emperor. The Persian emissary said:
"Our emperor asks if you would be agreeable to peace on the condition that the Tigris should be the boundary between you and us, so that whatever is with us on the eastern side of the Tigris remains ours and whatever you have gained on the western side is yours. And if this does not satisfy your land hunger, then nothing would satisfy you."
Saad the Muslim Commander-in-Chief told the emissary that the Muslims were not hungry for land; and that they were fighting in the name of Allah. He added that if the Persian emperor wanted peace it was open to him to accept Islam, or to pay Jizya. If both the alternatives were not acceptable then peace was out of question, and only the sword could decide the issue between them.
When the day dawned, it was found that the Persians had evacuated Bahrseer. In withdrawing the Persian garrison had destroyed all bridges on the Tigris. They had also taken away all the boats from the western bank of the Tigris, and anchored them on the eastern bank.
The Muslim forces occupied Bahrseer, The town was empty. All the residents had during the night managed to cross over to Ctesiphon on the other bank of the Tigris.