An interesting account from A.H.M Jones’ classic The Later Roman Empire, 284-602: a social, economic and administrative survey:
We possess a curious contemporary document. Jacob, a Palestinian Jew who arrived at Carthage in 634, was seized and forcefully baptised under a recent law of Heraclius. Pondering the Scriptures in prison he came to the same conclusion as the elder of the Jews at Sycaminon, and by his arguments persuaded the other Jews of Carthage that Jesus must have been the Messiah. Justus, another Palestinian Jew who arrived at Carthage at this juncture, upbraided him as a renegade, but Jacob asked him: ‘What do you think of the state of Romania? Does it stand as from the beginning, or has it been diminished?’ Justus replied dubiously: ‘Even if it has been somewhat diminished, we hope that it will rise again, because the Christ must come first, while the fourth beast, that is Romania, stands.’ But Jacob convinced him: ‘We see the nations believing in Christ and the fourth beast fallen and being torn in pieces by the nations, that the ten horns may prevail, and Hermolaus Satan, the Little Horn, may come.’
Justus added the convincing proof: the Little Horn had come. ‘My brother Abraham has written to me from Caesarea that a false prophet has appeared among the Saracens. “For when the candidatus Sergius was killed by the Saracens,” says Abraham, “I was at Caesarea, and I went by boat to Sycaminum; and they said, ‘the candidatus has been killed’, and we Jews had great joy. And they say that a prophet has appeared coming up with the Saracens and proclaims the coming of the anointed, the Christ who cometh. And when I Abraham came to Sycaminum, I went to the elder, a very learned man, and said to him: ‘What do you say, Rabbi, about the prophet who has appeared with the Saracens?’ And he groaned loudly and said: ‘He is false, for surely the prophets do not come with sword and chariot. Verily the troubles of today are works of confusion, and I fear lest the Christ who came first, whom the Christians worship, was himself he that was sent by God, and we shall receive Hermolaus instead of him. For Isaiah said that we Jews have hearts that have gone astray and been hardened, until all the earth be desolate. But go, Abraham, and enquire about the prophet that has appeared.’ And I Abraham made inquiry and learned from those that had met him, that you find nothing true in the so-called prophet, save shedding the blood of men; for he says that he holds the keys of paradise, which is untrue.” ‘ (Vol. 1, pp. 316-7)
The prophet who appeared with the Saracens was, of course, Mohammad; these were the beginning of the Islamic conquests of the Middle East and North Africa.