Islam teaches that people should be kind and tolerant of one another, and treat each other with respect. It also teaches that people should be modest, which is why many Muslim women cover their hair with a scarf. Islam also teaches that Muslims should be respectful of the other "people of the book," meaning Jews and Christians. This respect for the "people of the book" has a direct bearing on the story of Islam's arrival in Egypt.
When the armies of Islam came into Egypt in the year 640 C.E., the situation in Egypt was rather difficult. The Byzantine rulers did not like their Egyptian subjects, and the Egyptians hated the Byzantines. When the Muslims came, Babylon shut its gates and held out for seven months.
There are conflicting stories about exactly how the Muslims were able to conquer Egypt. One says that the Muslims won when they convinced the Copts to help them, and together they threw the Byzantines out of Egypt. Another says that it was the Chalcedonian Patriarch of Alexandria who let the Muslims have Egypt, since he thought that they would kill all of the Copts whose beliefs he found objectionable.
Babylon fell to the Muslim forces on the day after Easter, Monday April 9, 641. Once Egypt was under the control of the Muslims, the Copts found that their situation had actually improved. Muslims believe that Christians and Jews are People of the Book because they share belief in the same God, even if they have not accepted the Prophet Muhammad and his message. The Qur'an and hadith both set out provisions for situations where Muslims govern over People of the Book, and call for tolerance and good treatment. In Egypt, the Muslims were willing to let the Copts practice their religion and would leave them alone as long as they paid a poll tax every year. The poll tax was less than the yearly tributes and taxes the Copts had been required to pay to the Byzantines. The Copts also had the option of converting to Islam, but they were not forced to do so. Muslims did not constitute the majority of Egypt's population until around the 10th century C.E..