It is recorded regarding the victory over the Babylon Fort or Fustat that after gaining victory at Umm Dunayn, Hazrat Amr (ra) bin al-Aas marched towards the Babylon Fort and laid siege to it. Now this area is known as Fustat. The reason for it being called this is that in Arabic, tents are called “Fustat”. After successfully conquering the fort, Hazrat Amr (ra) bin al-Aas commanded to leave, and it so happened that a pigeon made a nest in Hazrat Amr’sra tent. When he saw it, he instructed that the tent should remain there and upon returning from Alexandria, he had a city established near the tent; and it subsequently became known as Fustat.
(Al-Faruq, Shibli Nomani, pp. 150-151, Dar al-Isha‘ah, Karachi, 2004)
It is estimated that the protective forces inside the fort were around 5,000 to 6,000 and they were armed in every way. Hazrat Amr (ra) began the siege of the Babylon Fort. After Alexandria, this was one of the strongest forts and had been built with cement blocks. It was surrounded by water from the Nile River. Since it was located on the Nile River, boats and ships would go straight to the door of the fort, and so it was essential for important work. The Arabs were not properly equipped to attack such a fort nor were they ready for this.
(Sirat Umar Faruqra, Muhammad Raza, pp. 264-265, Maktabah Islamiyyah, 2010)
And so, first and foremost, Hazrat Amr (ra) began making preparations to lay siege. Muqawqis, the ruler of Egypt, had already reached the fort before Hazrat Amr (ra) bin al-Aas and was preparing for battle. Hazrat Zubair (ra) rode his horse around all four sides of the ditch and would appoint the necessary number of soldiers to a given area. This siege continued for seven months straight, and the determination of victory or defeat could not be made.
(Al-Faruq, Shibli Nomani, p. 150, Dar al-Isha‘ah, Karachi, 2004)
During this time, sometimes the Byzantines would come out of the fort to fight but then would go back inside. All the while, Muqawqis would send his envoys to Hazrat Amr (ra) bin al-Aas in attempts to reconcile and strike fear.
Hazrat Amr (ra) bin al-Aas sent Hazrat Ubadah (ra) bin Samit for reconciliation with three conditions; either accept Islam or pay jizya, otherwise there would be a war. He said that a treaty should not be reached based on any other condition apart from these. Muqawqis agreed to pay jizya, and went himself to Heraclius to seek permission. However, Heraclius did not accept this and in fact became quite angry and expelled him from the land as a result.
(Sayyiduna Umar bin Khattab (ra) – Shakhsiyyat aur karnamey, Ali Muhammad Salabi, Urdu translation, p. 760, Al-Furqan Trust, Khangarh, Pakistan) (Hazrat Umar Farooq A‘zam, Muhammad Husain Haikal, translated by Habib Ash‘ar, pp. 582, 584, 590, Islami Kutub Khana, Urdu Bazar, Lahore)