Moslemism is the only great post-Christian religion of the world. Because it had its origin in the seventh century under Mohammed, it was possible to unite, within it, some elements of Christianity and of Judaism, along with particular customs of Arabia. Moslemism takes the doctrine of the unity of God, His majesty and His creative power, and uses it, in part, as a basis for the reproduction of Christ, the Son of God. Misunderstanding the notion of the Trinity, Mohammed made Christ a prophet announcing Him just as to Christians, Isaiah and John the Baptist are prophets announcing Christ.continue at The Catholic Gentleman
The Christian European West barely escaped destruction at the hands of the Moslems. At one point they were stopped near Tours and at another point, later on in time, outside the gates of Vienna. The Church throughout northern Africa was practically destroyed by Moslem power, and at the present hour, the Moslems are beginning to rise again.
If Moslemism is a heresy, as Hiliaire Belloc believes it to be, it is the only heresy that has never declined. Others have had a moment of vigor, then gone into doctrinal decay at the death of the leader, and finally evaporated in a vague social movement. Moslemism, on the contrary, has only had its first phase. There was never a time in which it declined, either in numbers, or in the devotion of its followers.
How exactly this takes place, I would love to find out.