Christianity Today: But what about the old saying, “The blood of the martyrs is the seed of the church”?
Historian Philip Jenkins: That was said by Tertullian, who came from the church in North Africa, where the church vanished. If you were to look at the healthiest part of Christianity right around the year 400 or 500, you might well look at North Africa, roughly what we call Tunisia and Algeria. It was the land of Augustine. Then the Arabs, the Muslims, arrive. They conquer Carthage in a.d. 698, and 100 years later—I don’t say there were no Christians there, but there certainly was only a tiny, tiny number. That church dies.
The rest is here: http://www.christianitytoday.com/ct/2009/march/24.52.html