When Umar received the report of Amr bin Al-Aas about the conquest of Babylon and the treaty with Maqauqas, he wrote back to say that he approved of the terms provided Heraclius agreed to submit to them. He desired that as soon as the reactions of Heraclius were known, he should be informed so that further necessary instructions might be issued.
Heraclius's reaction to the report of Maqauqas was violent. He remarked sarcastically that the Muslim force hardly numbered 12,000 while the Byzantine force in Egypt was five times as large leaving aside the Copts. Maqauqas was removed from the Viceroyship of Egypt, but he remained the Head of the Coptic Church. This was a matter in which the emperor could not interfere. Heraclius sent strict orders to the Commander-in-chief of the Byzantine forces in Egypt that the Muslims should be driven from the soil of Egypt.
Maqauqas waited on Amr and told him that Heraclius had repudiated the treaty of Babylon. Maqauqas assured Amr that so far as the Copts were concerned the terms of the treaty would be followed, but they were not responsible for the Byzantines. That was now an issue which the Muslims and the Byzantines might settle among themselves.
Maqauqas asked for three favours from the Muslims, namely:
1. Do not break your treaty with the Copts;
2. If the Byzantines after this repudiation ask for peace, do not make peace with them, but treat them as captives and slaves; and
3. When I am dead allow me to be buried in the Church of St. John at Alexandria.
This position was to the advantage of the Muslims. The Copts were the real natives of the land of Egypt. Both the Byzantines and the Muslims were strangers. Though some Copts from personal considerations continued to support the Byzantines, the sympathies of tho S::opts were now by and large with the Muslims. The Copts were not supposed to fight against the Byzantines on behalf of the Muslims but they undertook to help the Muslims in the promotion of war effort, help them in the provision of stores; build roads and bridges for them; and provide them moral support.
Under the circumstances the Muslim fight in Egypt was not against the Egyptians; it was against the Byzantines who were really intruders.
The Generals of the emperor mustered at Alexandria the capital of Egypt, and decided to wage a relentless war against the Muslims and drive them from Egypt.
Amr reported these developments to Umar, and Umar desired that before the Byzantines could gather further strength the Muslims should strike at them and drive them from Alexandria.
In February 641, Amr set off with his army from Babylon and the destination was Alexandria. On the third day of their march from Babylon the Muslims encountered a Byzantine detachment at Tarnut on the west bank of the Nile. Light action followed. The Byzantines could not hold the ground, and withdrew northwards to Alexandria.
While the main Muslim army halted at Tarnut, an advance guard under Shareek bin Sumayy was required to proceed forward. Twenty miles from Tarnut, Shareek came across a Byznatine detachment. The Byzantine force was very large, and it launched an attack on the Muslim advance guard thinking that they would be able to annihilate it. The Muslim advance guard fell back. The next day the Byzantine fell on the Muslim advance guard again, but in the meantime the main Muslim army had arrived and the Byzantines found safety in withdrawal.
The following day the Muslims resumed their march and reached Sulteis where they encountered a Byzantine detachment. Some hard fighting followed, but the Byzantine resistance soon broke down and they withdrew to Alexandria. The Muslims halted at Sulteis for a day and then resumed the march to Alexandria. Alexandria was still two day march from Sulteis.
After one day's march the Muslim forces arrived at Kirayun twelve miles from Alexandria. Here the Muslim advance to Alexandria was blocked up by a Byzantine detachment 20,000 strong. The strategy of the Byzantines was that the Muslims should be driven away before they actually arrived at Alexandria.
The two forces were deployed for action, and some hard fighting followed but the action remained indecisive. This state of affairs persisted for ten days. On the last day the Muslims launched a vigorous assault. The Byzantine resistance broke down, and they withdrew to Alexandria. The way to Alexandria having been cleared, the Muslim forces resumed the march from Kirayun and reached the outskirts of Alexandria some time in March 641 A D.