Occupation of Uballa. After winning the battle of Kazima, Khalid rested his men for a few days and then advanced further inland in Iraq. Khalid sent a contingent under Ma'qal bin Muqarrin to occupy Uballa. There were no Persian forces at Uballa, and the town was occupied without any resistance.
Hisn ul Mar'at. Muthanna with his column rode ahead of the main Muslim army. The task of this column was to reconnoiter and kill the strugglers left behind the retreating Persians.
North of Zubeir stood a fort known as "Hisn ul Mar'at" - the fort of the lady. A Persian princess Qamarzad who was related to the Persian emperor held it. Muthanna left a contingent under his brother Mu'anna to lay siege to the fort of the lady and himself proceeded with his column further north. Muthanna assaulted the fort and finding the resistance futile, Qamarzad surrendered. She was offered to accept Islam or to pay 'Jizya'. She accepted the first alternative and became a Muslim. Thereupon Mu'anna proposed marriage, and she married him.
The Persian Force. In the meantime another Persian army assembled at al-Madsen. It was placed under the command of a top ranking Persian General, Qarin bin Quryana. Like Hormuz, Qarin was also a 'one hundred thousand dirham' man. The original mission of Qarin was to march with his army to Uballa to reinforce Hormuz.
From al-Madain, the Persian army marched along the left bank of the Tigris. They crossed the Tigris at Mazar, and here they came to know of the defeat of the Persians at Kazima. Qarin camped at Mazar, and soon the remnants of the army of Hormuz who had escaped from Kazima joined the camp. They included the Generals Qubad and Anushjan who had commanded the wings of the army at Hormuz at Kazima.
Qarin was shocked that the imperial army of Persia under such a General as Hormuz should have been defeated by the uncouth Arabs. He resolved that he would avenge the defeat of Kazima and drive the Arabs to the desert.
Khalid's march to Mazar. The advance guard of Muthanna who scoured the countryside came to know of the Persian concentration at Mazar. Muthanna informed Khalid of such concentration. Qarin came to know that some Muslim forces were lurking in the neighborhood, and his plan was to fall on this Muslim force and destroy it, before it could get help from the main Muslim army. Khalid realized the danger that beset the column of Muthanna. Khalid was keen that he should destroy the Persian force under Qarin while the impact of the defeat at Kazima was still fresh in the Persian mind. By forced marches, Khalid reached Mazar in the third week of April 633 C.E. before Qarin could take any action against the column of Muthanna.