After the battle of Namaraq, the defeated Persian force who survived sought refuge with Narsi at Kaskar. Narsi was a cousin of the Kisra Puran Dukht and Kaskar was his estate. Kaskar was the Tigris downstream of Ctesiphon the capital of Persia. It was about two hundred miles from Namaraq across the entire Doab between the Euphrates and the Tigris.
Narsi had a good concentration of force at Kaskar. With the coming of the Persian forces who had been defeated at Namaraq the strength of the Persian forces at Kaskar further increased. The Persian Commander-in-Chief promised to send some more Persian forces under the command of Jalinus to Kaskar. With these forces at his disposal, Narsi felt secure at Kaskar. Kaskar was so far away from the Muslim camp that Narsi felt that no Muslim attack could be imminent.
Abu Ubaid, the Muslim commander, thought otherwise. He thought that it would have a good psychological effect if in the wake of the battle of Namaraq the Muslims rushed to Kaskar and deal with the Persian forces there before the forces under Jalinus could come to their assistance. Abu Ubaid accordingly ordered a march across the Suwad to Kaskar. Dashing across the Suwad the Muslim forces appeared before Kaskar. The two forces met at Saqatia a few miles from Kaskar. The strategy of the Persians was to defer action till the arrival of the force under Jalinus. The strategy of the Muslims was to press the attack and force immediate decision.
The right wing of the Persian army was commanded by Banduyah and the left wing by Tairuyah. Both of them were the cousins of Kisra. Abu Ubaid launched the attack. The battle was hotly contested. No details about the battle are available. All that we know is that the Persians were defeated, and those who survived retreated to Ctesiphon. Immense booty fell to the Muslims. The most prized possession that the Muslims got was the Narsi garden which was known throughout Persia for its delicious fruit. The fruit of the garden were heretofore reserved for Narsi, and he sent occasional gifts to the Kisra. On getting hold of the garden the Muslims distributed the fruit among all soldiers. Some fruit was also sent to Umar to taste.
Abu Ubaid stayed at Kaskar but he sent Muslim contingents in the adjoining areas to bring the people under Muslim rule. Muthanna was sent with his force to the region of Barosma. Walid was sent against Zawabi Asim was sent against Nahrjubar. No resistance was offered anywhere. The chiefs of these places waited on Abu Ubaid at Kaskar and offered submission. They also offered him some delicious food. He asked whether this food was meant for the entire Muslim army. The chiefs stated that the food was meant for him and his officers and that they would give a feast for the army later. Thereupon Abu Ubaid refused to accept the food and returned it with the remarks that as the General of the Muslim army he could only eat what the common soldiers ate.
In the meantime the Persian force under Jalinus advanced. While the Persian force was still in the territory of Barosma, Abu Ubaid advanced from Kaskar to meet it. The two forces met at Baqsiasa after a hot contest the Persians were defeated and they retreated after leaving many soldiers dead on the battle-field.
Abu Ubaid wrote to Umar a detailed report of the battles of Kaskar and Baqsiasa. Umar in reply advised Abu Ubaid in the following terms:
"You have entered the land of trickery and guile, dishonesty and oppression. You have marched against a people who love evil and know it well and abjure goodness of which they are ignorant. So be on your guard and watch your tongue. Reveal not your secrets for those who guard their secrets are secure against unpleasantness and loss."