Amr ibn al-As, having 4000 horsemen set out to conquer Egypt. Egypt was under the rule of Byzantine Emperor Heraculas. Byzantinians were beaten and lost the control of Fayyum and Helliopolis (640). Amr marched on. Defeated Byzantine forces gathered at the fortress of Babylon. .Amr lured them out and defeated them there also

Patriach Cyurs, who was the civil governor of the country, seeing critical situation began negotiations for peace and sought approval of his conduct from Heraculas. The Emperor rejected the peace pact and took Cyrus as traitor. The Emperor died in February 641 and Cyrus was able to conclude peace, after the surrender of Babylon in the same year (20 A.H.). Egypt, except Alexandria, came under the control of Muslims. New Emperor Constantine III sent down a large army to defend. Amr moved towards Alexandria and with his valour and skill defeated the Byzantine forces again. Alexandria was brought under Muslims control now. Caliph Osman made Amr governor of Egypt.