Originally posted by straffo
you can dig a bit because I don't think it was so simple.
I don't know about simple but it I think the following is about how how it went: (borrowing most of this, correct me if it's wrong)
"Caliph Omar conquered Jerusalem in 638, the city had been Christian for over 300 years. Soon after, the Prophet's disciples invaded and destroyed the glorious churches of Egypt, first, and then of North Africa, causing the extinction of Christianity in places that had had bishops like St Augustine."
"By the end of the 10th century, the spread of Islam had all but stopped and a comparatively stable state of affairs existed between Muslims, Jews and Christians with the latter able to make pilgrimages to Jerusalem, which was at that stage under Muslim rule.
This state of affairs came to an end however, with the aggressive expansion of the Turks who were ambushing parties of Christian pilgrims on their way to Jerusalem. The various routes to Jerusalem had been relatively safe and these sudden attacks alarmed the European Christians for whom pilgrimages were very important."
Then we have some back and forth fighting, conquering, attrocities by both sides, etc.... However, some say that the Muslims were in all cases the aggressors as the Christians only fought to take back what had been taken from them and they never attacked Arabia while the Muslims did attempt to conquer foreign lands.
Anyhow, lot more to it than that but I don't believe that what I just presented is inaccurate. Of course, while I may be pretty old I can't give a first hand account.