The Arab conquest of Egypt, led by the army of Amr ibn al-As, under the Rashidun Caliphate took place between 639 and 642 AD. It ended the Roman period in Egypt which began in 30 BC and lasted for seven centuries, and more broadly, the Greco-Roman period which lasted for about a millennium.
Prior to the conquest, Byzantine rule in the country had been shaken, as Egypt had been conquered and occupied by the Sasanian Empire for a decade between 618–629, before being reconquered by the Byzantines under emperor Heraclius. The Caliphate took advantage of Byzantines' exhaustion to invade Egypt.
During the mid-630s, the Romans had already lost the Levant and its Ghassanid allies in Arabia to the Caliphate. The loss of the prosperous province of Egypt and the defeat of the Byzantine armies severely weakened the empire, resulting in further territorial losses in the centuries to come.
Background
In 640, Heraclius was the Byzantine emperor, Cyrus of Alexandria was both the government-appointed Chalcedonian Patriarch of Alexandria and de facto governor of Egypt, and Theodore was the commander-in-chief of the Byzantine army in the province. The majority of the Egyptians were non-Chalcedonian Oriental Christians who recognised Pope Benjamin I as their rightful Pope and Patriarch of Alexandria rather than Cyrus.
Since the time of the Byzantine Emperor Justinian I, Egypt was administratively divided into four provinces under the control of the general ruler of the East in Constantinople. These provinces were Aigyptiaca (Alexandria and the western Delta), Augustamnica (the eastern Delta until Arish in northern Sinai), Arcadia (Middle Egypt to Oxyrhynchus) and Thebaid (Upper Egypt starting at Hermopolis). Each of these provinces was headed by a Pagarch (prefect). This division resulted in divided accountability for Egypt, which contributed to its defeat to both the Sasanian invasion (618–621 AD) and the Arab invasion (641 AD).
Following the death of Muhammad in 632 AD, the Arab armies of the Rashidun Caliphate began expanding toward both Sasanian Persia and the Byzantine Empire. Neither of the two former powers was prepared for the aggressive expansion of the Arabs, as both largely underestimated them. This is best depicted by the ambivalent views held by the Byzantines and the painstakingly slow reaction of the Sasanians.
After defeating the Byzantines at Yarmuk (636 AD) and the Persians at al-Qadisiyyah (637 AD), the gaze of the Arab generals turned towards the riches of Byzantine Africa. After the Siege of Jerusalem, it was Amr ibn al-As who suggested an invasion of Egypt to the Caliph Umar, being familiar with the country's prosperity both from visiting it as a merchant and from leading the expedition to Gaza in 637. Appealing to the Caliph, he said "the conquest of Egypt will give great power to the Muslims and will be a great aid to them, for it is the wealthiest land and the weakest in fighting and war power."
After being convinced by Amr to proceed with the invasion, Umar is said to have had "an eleventh-hour change of heart", but too late to stop it. This element of the story, which conveys the caliph's wariness at allowing a general to seize such an asset, may have been a later embellishment in light of Amr's subsequent reputation as a stubbornly independent governor.
For three years after the Muslim conquest of Syria, Cyrus had been paying them tribute not to invade Egypt.
Rashidun invasion of Egypt
Crossing the Egyptian border
In December 639, Amr ibn al-As left for Egypt with a force of 4,000 troops. The invading army included units from various Arab tribes, especially from Yemen. Most of the soldiers belonged to the Arab tribe of 'Ak, but Al-Kindi mentioned that one third of the soldiers belonged to the Arab tribe of Ghafik. The Arab army also contained many apostates whom the Caliph Abu Bakr forced back into Islam during the Ridda Wars. These were encouraged by Abu Bakr's successor, Umar ibn al-Khattab, to join the conquests as a way to tempt them to gain bounty and to keep them away from seditious activities. On the way to Egypt through northern Sinai and along the Mediterranean coast, the Arab soldiers were also joined by numerous bedouins from Sinai and the Eastern Desert, Nabataeans, some Roman and Persian converts to Islam, as well as bandits and vagabonds. Amr ibn al-As enticed these various groups by promising them war booty, spoils and captives in return for their help in battles leading to the invasion. In total, the invaders numbered between twelve and fifteen thousand men.
However, Umar, the Muslim caliph, reconsidered his orders to Amr and considered it unwise to expect to conquer such a large country as Egypt with a mere 4,000 soldiers. Accordingly, he wrote a letter to Amr ordering him to "return with all haste to the court of the Caliph, so that his soldiers might join additional campaigns being planned elsewhere". However, there was a provision in the letter stating that Amr's first duty was the protection of his troops, and if he found himself on Egyptian soil by the time he received the letter, the Caliph would leave overall strategic command of movement to him, so as to not unduly burden troops already in the field.
The messenger, Uqba ibn Amir, caught up with Amr at Rafah, a little short of the Egyptian frontier. Guessing what might be in the letter, Amr ordered the army to quicken its pace. Turning to Uqba, Amr said that he would receive the caliph's letter from him when the army had halted after the day's journey. Uqba, unaware of the contents of the letter, agreed and marched along with the army. The army halted for the night at Shajratein, a little valley near the city of Arish, which Amr knew to be beyond the Egyptian border. Amr then received and read Umar's letter and went on to consult his companions as to the course of action to be adopted. The unanimous view was that as they had received the letter on Egyptian soil, they had permission to proceed.
When Umar received the reply, he decided to watch further developments and to start concentrating fresh forces at Medina that could be dispatched to Egypt as reinforcements. On Eid al-Adha, the Muslim army marched from Shajratein to Arish, a small town lacking a garrison. The town put up no resistance, and the citizens offered allegiance on the usual terms.
Conquest of Pelusium and Bilbeis
According to a legend related by al-Waqidi, Cyrus of Alexandria had a beautiful daughter named Armenousa, whom he sought to marry to Heraclius Constantine. Constantine accepted the marriage proposal, so in late 639 Armenousa left Babylon in a grand marriage procession which included two thousand horsemen, along with slaves and a long caravan laden with treasures that served both as dowry and tribute. On her way to Constantine, who was in Caesarea, she heard of the Arab army approaching Egypt and dispatched a regiment of her guards to defend Pelusium, a garrison city considered to be the eastern gateway to Egypt at the time, while she herself remained in Bilbeis with more of her guards and sent warnings to her father Cyrus. However, Alfred J. Butler dismisses Armenousa's story as a myth.
In December of 639 or early January 640, the Muslim army reached Pelusium. The siege of the town dragged on for two months. In February 640, an assault group, led by the prominent Huzaifah ibn Wala, successfully captured the fort and city.
The losses incurred by the Muslim army were ameliorated by the number of Sinai Bedouins, who had joined them in conquering Egypt, out of a desire for plunder. The Bedouins belonged to the tribes of Rashidah and Lakhm.
The ease with which Pelusium fell to the Muslims and the lack of Roman reinforcements during the month-long siege is often attributed to the treachery of Cyrus, who was also the Greek Patriarch of Alexandria (not the one recognised by most of the population, who was Pope Benjamin I).
After the fall of Pelusium, the Muslims marched to Bilbeis, 65 km (40 mi) from Memphis via desert roads, and besieged it. Bilbeis was the first place in Egypt that the Byzantines showed some measure of resistance towards the Arabs. Two Christian monks, accompanied by Cyrus of Alexandria and the famous Roman general Aretion, came out to negotiate with Amr ibn al-As. Aretion had been the Byzantine governor of Jerusalem, but had gone to Egypt shortly after losing the Battle of Ajnadayn. Amr gave them three options: convert to Islam, pay the jizya, or fight. They requested three days to reflect and then, according to Al-Tabari, requested two extra days.
At the end of the five days, the two monks and the general decided to reject Islam and the jizya and fight the Muslims, thus disobeying Cyrus, who wanted to surrender and pay jizya. Cyrus left for the Babylon Fortress. The battle resulted in a Muslim victory during which Aretion was killed and Armenousa was captured, but sent back to Cyrus. Amr ibn al-As subsequently attempted to convince the native Egyptians to aid the Arabs and surrender the city, based on the kinship between Egyptians and Arabs via Hajar. When the Egyptians refused, the siege resumed until the city fell around the end of March 640.
Siege of Babylon Fortress
Amr had assumed that Egypt would be a pushover but was quickly proven wrong. Even at the outposts of Pelusium and Bilbeis, the Muslims had met stiff resistance, with sieges of two and one months, respectively. As Babylon, near what is now Cairo, was a larger and more important city, resistance on a larger scale was expected. The Muslims arrived at Babylon some time in May 640.
Babylon was a fortified city, and Theodore had indeed prepared it for a siege. Outside the city, a ditch had been dug, and a large force was positioned in the area between the ditch and the city walls. The Muslims besieged the fort, a massive structure 18 m (59 ft) high with walls more than 2 metres (6.6 feet) thick and studded with numerous towers and bastions and a force of some 4,000 men. Early Muslim sources place the strength of the Byzantine force in Babylon at about six times the strength of the Muslim force. For the next two months, fighting remained inconclusive, with the Byzantines repulsing every Muslim assault.
Realising that Babylon was too strong to take, Amr sent a detachment to raid the city of Faiyum. The Byzantines had anticipated that and so had strongly guarded the roads that led to the city and had fortified their garrison in the nearby town of Lahun. At this time, the governor of Faiyum was Domentianus, while Theodosius was the prefect of its province, Arcadia Aegypti, and Anastasius was the prefect of Alexandria (and by extension the de jure governor of Egypt). The defence of Arcadia Aegypti was entrusted to a certain John, whom Hermann Zotenberg identifies with the John, Duke of Barca or Barcaina mentioned by Nicephorus. He had brought the Ecthesis and a portion of the True Cross from Patriarch Sergius to Cyrus, and was likely on a direct commission from Emperor Heraclius.
When the Muslims realised that Faiyum was also too strong for them to take, they headed towards the Western Desert, where they looted as many cattle and animals as they could. They subsequently headed to a town in the Faiyum district named Bahnasa (not to be confused with Oxyrhynchus 50 miles further south), which was defeated and the city was captured. According to John of Nikiû, "they compelled the city to open its gates, and they put to the sword all that surrendered, and they spared none, whether old men, babe, or woman." The Arabs then noticed that John, with a small group of 50 men, had been following them. John and his men retreated to their base at Abûît, but their hiding place was betrayed by a Bedouin chief and they were all killed.
When news of John's death reached Theodore, who was commanding the garrison at Babylon, 'his lamentations were more grievous than the lamentations of David over Saul when he said: "How are the mighty fallen, and the weapons of war perished!"' as John of Nikiu puts it. Theodore hurried his troops up the Nile while Anastasius and Theodosius rushed from Nikiû to Babylon to strengthen it, while a further force was sent from Babylon to Abûît to strengthen it under Leontius, who was "obese in person, quite without energy and unacquainted with warlike affairs". When he arrived, he found Theodore and his troops there already making sorties every day against the Arab base at Bahnasa. Judging that Amr would soon be defeated, Leontius left only half of his men there, going back to Babylon with the other half.