After the occupation of Bahrseer, only the Tigris half a mile wide lay between the Muslims and Ctesiphon. The river was in flood and there were no means with the Muslims to cross it. In their withdrawal from Bahrseer the Persians had taken away all the boats. The approaches to Ctesiphon were heavily guarded by the Persians. It was reported that there was considerable Persian force in Ctesiphon under the command of Generals Mihran and Khurrazad. Khurrazad was a brother of the General Rustam who had been killed in the battle of Qadisiyya.
Some Persians who had accepted the Muslim rule volunteered to show Sa'ad a site downstream where the river could be forded. Sa'ad saw the site, but was not sure whether it was fit for crossing. The Arabs were land warriors and they hesitated to negotiate water. That night Saad had a dream in which another site was indicated to him which the Muslims could cross.
The next morning Sa'ad asked for volunteers who could cross the river on horseback. Asim was the first to volunteer. Then others offered themselves. Sa'ad went to the site which he had seen in the dream, and after invoking the blessings of God asked the six hundred warriors led by Asim to plunge into the river and cross over to the other bank.
The Muslim horses plunged in the river and slowly proceeded to the other bank. When the Persians saw that the Muslims were coming, tbe Persian horses also plunged in the river to hold back the Muslims from crossing the river. When the Muslims were hardly half way in the river they faced the Persians. A river battle ensued. In the hand to hand fight that followed the Muslims were able to kill many Persians and the rest fled away. As the Muslims landed on the eastern bank of the Tigris, a cry went around the Persian camp, "The Muslims have come: they are not men, they are devils and jinns. Who can fight them?"
After the first band of six hundred volunteers under Asim, other contingents crossed the river, and this process went on till all the Muslim forces had crossed over to the other side of the Tigris. When the Persian Generals came to know that the entire Muslim force had crossed over to Ctesiphon in spite of the flood in the river, they decided that they should evacuate Ctesiphon as further resistance was futile. The Persian army evacuated the city. The Persian emperor Yazdjurd retreated to Hulwan. While withdrawing the Persian emperor carried away as much of the imperial treasure and other valuable possessions as he could carry.
From the river bank the Muslim forces marched to the city of Ctesiphon. The march was led by the column of Asim. Me was immediately followed by the column of Qaqa. Then other columns marched in military order. At one place a few Persian soldiers offered resistance but they were soon cut off. The Muslim columns marched through the heart of Ctesiphon. All business premises were closed. No Persians were seen, and the Muslims met no resistance. The Muslims got to the White Palace the seat of the Persian Government. A small Persian regiment stationed there offered some resistance. Salman the Persian who was with the Muslim troops advised the Persian regiment to submit in its own interest as they could no longer face the Muslims. The garrison surrendered, and the White Palace was occupied by the Muslims.
After occupying the city, Sa'ad announced amnesty to all Persians who were in the city. A delegation of the representatives of the people waited on Saad. They sought terms, and the usual terms being offered they agreed to the imposition of Jizya. A regular peace pact was drawn up, and the citizens were called upon to follow their normal avocations. Without any large scale fighting the Muslims had conquered Ctesiphon, the capital of the once mighty Persian empire.
Sa'ad moved into the White Palace and established his headquarters there. The great courtyard of the palace was converted into a mosque where Sa'ad led a mass victory prayer.
Sa'ad next sent out columns in several directions to deal with the Persian stragglers. One column took the route to Hulwan. They caught up some Persians at Nahrawan and recovered the valuable goods that they were carrying. These included the fabulous crown of Persia, the imperial regalia and several ornaments. The booty comprised enough gold and precious stones to purchase a kingdom. Another column operating in another sector recovered some swords and other valuable armour. Another Muslim column captured some chests which contained a horse of gold studded with sapphires and emeralds.
Within Cteiiphon the Muslims found a pavilion containing a large number of sealed baskets. These baskets contained utensils of gold and silver. From the imperial treasury the Muslims got cash of over a billion dirhams.
When the booty was distributed among the soldiers the share of each man came to 12,000 dirhams. Among the booty was a grogeous carpet found from the White Palace. It was a huge bulky affair 900 meters square. It was worked with gold and gems. lt represented a garden with glades, trees and flowers. The branches of the tree were that of gold, the leaves were of silver, and the fruit were of gems. It was one of the wonders of the world. As it could not be distributed among the soldiers, Sa'ad sent it to Madina along with the usual onefifth State share.