Islam saved Jewry. This is an unpopular, discomforting claim in the modern world. But it is a historical truth. The argument for it is double. First, in 570 CE, when the Prophet Mohammad was born, the Jews and Judaism were on the way to oblivion. And second, the coming of Islam saved them, providing a new context in which they not only survived, but flourished, laying foundations for subsequent Jewish cultural prosperity – also in Christendom – through the medieval period into the modern world.
By the fourth century, Christianity had become the dominant religion in the Roman empire. One aspect of this success was opposition to rival faiths, including Judaism, along with massive conversion of members of such faiths, sometimes by force, to Christianity. Much of our testimony about Jewish existence in the Roman empire from this time on consists of accounts of conversions.
Great and permanent reductions in numbers through conversion, between the fourth and the seventh centuries, brought with them a gradual but relentless whittling away of the status, rights, social and economic existence, and religious and cultural life of Jews all over the Roman empire.
A long series of enactments deprived Jewish people of their rights as citizens, prevented them from fulfilling their religious obligations, and excluded them from the society of their fellows.
Had Islam not come along, Jewry in the west would have declined to disappearance and Jewry in the east would have become just another oriental cult.