This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The Muslim Conquest of Egypt was led by the general Amr ibn al-As under the direct authority of Caliph Umar himself. The invasion force crossed from Palestine into the Nile Delta in 639, and Amr's own forces defeated the Byzantine garrison at the Battle of Heliopolis in 640 before besieging the fortress of Babylon, near modern Cairo, a siege that opened the way deeper into the Egyptian interior beyond it.
Amr went on to capture the great city of Alexandria itself in 641 following a negotiated surrender rather than an assault, and a brief Byzantine attempt to retake Alexandria by sea in 645 to 646 was repelled by the caliphate's own forces, securing Egypt permanently under caliphal rule after Emperor Heraclius's own death in 641 had already passed Byzantine authority to his successors. Egypt became one of the wealthiest and most important provinces of the whole caliphate, valued especially for its rich grain production along the Nile. Alexandria's own capture in particular gave the caliphate control of one of the ancient Mediterranean world's great cities, its library and scholarly reputation long past their classical peak but its harbor and administrative apparatus still fully intact for the new rulers to inherit rather than rebuild from nothing. The whole campaign, from the Delta crossing in 639 to the repulsed Byzantine counterattack in 646, took barely seven years to secure permanently.