Early Islamic Period in Egypt
Islamic History in Egypt starts in 639, Khalifa Omar dispatched a 4,000-strong army to Egypt under the command of Amr Ibn Al-Aas, followed by a 5,000-strong force in 640, which defeated the Byzantine army at the battle of Heliopolis. The Byzantine army withdrew to Amr in a pact made in November 941, and he continued to Alexandria. From 941 to 946, a series of conflicts resulted in the re-conquest of Alexandria by the Byzantine Empire in 645, until the Muslims re-took it in 946. Constans the second sent another expedition in 654 to reclaim Alexandria, but no other attempts to take sovereignty of the land were made after that.

Amr Ibn Al- Aas Mosque by Manshy482
Following the first defeat of Alexandria, Amr found a new location for his forces to dwell near the Byzantine Fortress of Babylon, which he named Fustat. In Coptic Cairo, both the remnants of this fort and the location of the mosque itself can still be visited today (Old Cairo). Up until the contemporary era, Egypt was ruled by a succession of Muslim governments. The Umayyad Caliphate, centered in Damascus, succeeded the Rashidun Caliphate.
Umayyad Period
Through the many islamic regimes, the Umayyad Caliphate was one of the most prominent Islamic caliphates. As a result, the state’s leader was known as the caliph, who was also the son of the great caliph.
From 661 to 750 CE, the Islamic Empire was managed by the Umayyad Caliphate. When Muawiyah I became Caliph after the First Muslim Civil War, it followed the Rashidun Caliphate. Muawiyah I established his capital in Damascus, from where the Umayyads managed the Islamic Empire for nearly a century. When the Abbasids claimed the authority in 750 CE, the Umayyad Caliphate came to an end.

Ibn Tulun Mosque, by Bakar_88
From 661 to 750 CE, the Islamic Empire is ruled by the Umayyad Caliphate. After the first Muslim civil war, Muawiyah was elected Caliph. Muawiyah built Damascus as the capital, and ruled for about a century. When the Abbasids acquired control in 750 CE, everything came to an end.
Abbasids Period
After a revolution against the Umayyads in the eighth century, the Abbasid Caliphate was established in Baghdad. The Fatimid Caliphate, which originated in modern-day Tunisia, took control of Egypt from the Abbasids in the 9th century and founded a new capital called Al-Qahirah, from which modern-day Cairo gets its name. The Fatimid Caliphate fell to the Ayyubid Caliphate in 1171 AD, which was formed by Salah Ad-Din, a legendary Crusader general.
Egypt remained an important element of the Muslim world throughout all of these changes in administration. The Nile Valley, like the Roman and Greek empires before it, was a major grain producer. Furthermore, Egypt and its capital, Cairo, were of tremendous geographic and political significance during the Fatimid and Ayyubid Caliphates. The gorgeous buildings that still adorn Islamic Cairo are proof of the riches and power that came with Cairo’s status as the capital of these powerful regimes. The Egyptian people, like their government, changed over the years. Egyptians gradually turned to Islam.
Non-Muslims faced a severe tax burden at times, in contrast to the Rashiduns’ gentle treatment of non-Muslims, making conversion a viable option. Conversion rates spiked during the Crusades when the war between European Christians and Muslim rulers made religion more political; yet, it’s impossible to pinpoint exactly when Islam surpassed Christianity as Egypt’s most popular religion.
Following the fall of the Abbasids, several Islamic dynasties rose to power, including the Tulunids, Second Abbasids, Ikhsidids, Fatimids, Ayyubids, Mamluk Egypt, and the Bahri dynasty.
Byzantine Rule
Islam’s introduction in Egypt was perfectly timed. After being briefly occupied by the Persian Sassanid Empire, Egypt was only recently regained by the Byzantine Empire. Furthermore, due to a theological difference between the Coptic Church and the Byzantines, the Egyptian Coptic Christian majority was persecuted by their Byzantine authorities.
The Byzantines’ determination to eradicate this diverse theology in Egypt made it simple for Egyptian Christians to embrace the Muslim conquest, as the Rashidun Caliphate simply required non-Muslims in conquered territories to pay a levy in exchange for being exempt from military service in the Rashidun troops.