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.

[3] Neither of the two former powers was prepared for the aggressive expansion of the Arabs, as both largely underestimated Islam and its growing support; this is best depicted by the ambivalent views held by the Byzantines and the painstakingly slow reaction of the Sasanians.

After the Siege of Jerusalem, it was Amr ibn al-As who suggested an invasion of Egypt to the Caliph,[1] being familiar with the country's prosperity both from visiting it as a merchant and from leading the expedition to Gaza in 637.

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.

[6] 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.

[8] 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.

[9] 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".

[citation needed] When Umar received the reply, he decided to watch further developments and to start concentrating fresh forces at Madinah that could be dispatched to Egypt as reinforcements.

[16][17][18][19][20][21] The losses incurred by the Muslim army were ameliorated by the number of Sinai Bedouins, who, taking the initiative, had joined them in conquering Egypt.

[23] 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).

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.

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.

[15] In July, 'Amr wrote to 'Umar requesting reinforcements, but before the letter reached him, the caliph had already dispatched 4,000 men, mostly veterans of the Syrian campaigns, to bolster Amr's strength.

Then, with negotiations stalled, during the night of 20 December, a company of handpicked warriors, led by Zubayr, managed to scale the wall, kill the guards, and open the gates for the Muslim army to enter.

[15] The final assault of the Muslims was on Good Friday, April 6 641, and by Easter Monday the Roman troops had evacuated and began marching to Nikiû.

Many Copts who were imprisoned in Babylon, either for refusing to accept Chalcedon or on suspicion of treachery, were released from prison by the Romans, but Eudocianus, the brother of Domentianus, had them scourged and their hands cut off.

[35] Upon hearing about this, Heraclius was furious and sent Cyrus a letter full of insults, calling him an abject coward and a heathen and asking whether 100,000 Romans were a match for 12,000 barbarians.

The Muslim commanders decided to halt the main army at Tarnut and send an advance guard of cavalry forward to clear the path.

[citation needed] Heraclius died in February 641, two months before the fall of the Babylon Fortress, and was succeeded by his two sons Constantine III and Heraclonas as co-emperors.

She had Heraclonas give Cyrus express permission to make peace at any price with the Arabs, but also gave him reinforcements and a new general named Constantine to replace John.

[15] When Theodore returned to Alexandria, he dismissed Domentianus as the military commander of the garrison and exiled him from the city, replacing him with Menas, who was a non-Chalcedonian Copt and popular with the army.

Their entire path was covered in carpets, hymns were sung, and a piece of the True Cross which was earlier brought to Egypt by John, Duke of Barcaina, and stored by the monks of Tabenna, was carried with Cyrus and Theodore.

The local populace was not informed of it until an Arab army approached Alexandria to receive the tribute, and the Byzantine generals told the people not to resist.

Realising what had happened, a furious mob attempted to stone Cyrus, but he said to them "I have made this treaty in order to save you and your children" and wept before them, which calmed the riot down.

He began building his new capital, Fustat, just outside Babylon, and the Byzantine prefects and governors of Egypt either converted to Islam to retain their positions, or were replaced by Muslims.

[40][page needed] 'Uqbah ibn Nafi, who later made a great name for himself as the conqueror of Africa and led his horse to the Atlantic, had an unhappy experience in Nubia.

[41] In 645, the newly installed Eastern Roman Emperor Constans II was determined to retake the land, and ordered a large fleet to carry troops to Alexandria.

These troops, under Manuel, took the city by surprise from its small Arab garrison towards the end of 645 in an amphibious attack - thus temporarily winning Alexandria back.

With Umar's permission, Amr decided to build a canal to join the Nile with the Red Sea to open new markets for Egyptian merchants and an easy route to Arabia and Iraq.