Battle of Heliopolis (Conquest of Egypt)

The Battle of Heliopolis was the decisive engagement that broke Byzantine power in Egypt and opened the way to Alexandria and full Muslim control of the country. Amr ibn al-As had entered Egypt in 639 CE with Caliph Umar's reluctant permission, his original force of only about 4,000 later reinforced by Zubayr ibn al-Awwam and others. After an initial victory at Pelusium and a prolonged siege of Babylon fortress, the main Byzantine field army under Theodore met the Muslims at Heliopolis — ancient 'City of the Sun' near modern Cairo. The Byzantine force was routed. The fall of Heliopolis was followed by the surrender of Babylon fortress in April 641. Amr then advanced on Alexandria. The Coptic Christian population, deeply resentful of Byzantine religious persecution, provided intelligence and sometimes assistance to the Muslim forces. The conquest of Egypt gave the emerging Muslim state control of the wealthiest grain-producing province of the ancient Mediterranean world.