We know very little about the initial reactions to Islam - it was a chaotic time for the empire and we lack the sources to say anything definitive. Moreover, different Romans had different views about Islam, especially as the empire at this point was still a superpower with interests across the Mediterranean world. Popes, Arab frontiersmen, Egyptian peasants, Armenian princes and more were all subjects of the emperor, yet they all saw Islam very differently because they all had their own separate interests and needs. It was a complicated time and we certainly can't generalise about a 'typical' reaction to Islam, especially as almost immediately upon hearing about Islam the eastern provinces were attacked and taken. Having said that, I will still try to piece together the earliest fragmentary sources and present some contemporary perspectives, but do bear in mind that this is by no means definitive (or accurate for that matter).

The earliest mention of Islam is from a Roman propaganda pamphlet written around 634, The Teachings of Jacob the Newly-Baptised. Essentially, the text was written to urge Jews to remain loyal to the empire and to convert to Christianity. Why was this important? Well, after his surprising victory against Persia in the war of 602-628, emperor Heraclius embarked on a programme of religious unification within the empire, one which involved talks with miaphysite Christians, who were dominant in Egypt and Syria (whereas Chalcedonian Christianity was generally the brand of Christianity favoured in the rest of the empire), and the issuing of edicts against the Jews. It was in this milieu that Islam swept onto the scene and from this source it is clear that Roman authorities, even in Carthage, were worried about potential unrest as a result of military failure. Within this pamphlet, Jacob (a Jewish convert to Christianity) and his friends essentially argued that North African Jews should not believe the rumours of Roman defeats coming in from the east:

Justus answered and said, “Indeed you speak the truth, and this is the great salvation: to believe in Christ. For I confess to you, master Jacob, the complete truth. My brother Abraham wrote to me that a false prophet has appeared. Abraham writes, ‘When [Sergius] the candidatus was killed by the Saracens, I was in Caesarea, and I went by ship to Sykamina. And they were saying, “The candidatus has been killed,” and we Jews were overjoyed. And they were saying, “A prophet has appeared, coming with the Saracens and he is preaching the arrival of the anointed one who is to come, the Messiah.”

And when I arrived in Sykamina, I visited an old man who was learned in the scriptures, and I said to him, “What can you tell me about the prophet who has appeared with the Saracens?” And he said to me, groaning loudly, “He is false, for prophets do not come with a sword and a war-chariot. Truly the things set in motion today are deeds of anarchy, and I fear that somehow the first Christ that came, whom the Christians worship, was the one sent by God, and instead of him we will receive the Antichrist. Truly, Isaiah said that we Jews will have a deceived and hardened heart until the entire earth is destroyed. But go, master Abraham, and find out about this prophet who has appeared.” And when I, Abraham, investigated thoroughly, I heard from those who had met him that one will find no truth in the so-called prophet, only the shedding of human blood. In fact, he says that he has the keys of paradise, which is impossible.’ These things my brother Abraham has written from the East.”

This text is interesting in several ways. The most important being the mention of an anonymous prophet waging war against the empire and who seemingly gathered the support of some Jews. The second thing to note here is the emphasis on the apocalypse, which isn't that odd, since late antiquity was a period when apocalyptic writings (whether Christian or Jewish) flourished; in that sense, Islam fits rather well into the existing intellectual context. Lastly, this source shows at least one way the Roman government responded to this new prophet, as presumably the fear of a Jewish fifth-column was real even in North Africa, many miles away from where the battles were being fought; what then does this say about what the Romans were doing in Syria and Palestine? We have no obvious sources for their immediate reactions apart from their military response, but this is a question I don't think historians have explored enough.

Another contemporary source is a sermon by Patriarch Sophronius of Jerusalem, who lamented to his congregation about the fact that they weren't able to travel to Bethlehem in 634 to celebrate the Nativity due to Arab raiders. However, his characterisation of the Arabs as barbarous and generally unpleasant had a long and proud history in the Roman Empire, as the Romans were never fans of anyone who didn't live within the empire, so this does not necessarily mean that Sophronius was angry at the Arab raiders because of their religion. It is also strange because Arab auxiliaries had guarded the Roman frontier with Arabia for centuries by this point, with some groups, such as the Ghassanid confederation, being very powerful indeed and played a major role in affairs within the empire itself. Realistically, Romans living in the east were aware of Arabs and must have co-existed with them; viewed from this perspective, the rise of a new Arab monotheistic movement that tolerated Christianity wasn't that dramatic of a change for these Romans. Excessive hyperbole was pretty standard for ecclesiastical writers at the time, so we shouldn't treat this as a particularly accurate account of what local Christians thought. It is unfortunate then that the majority of our sources for early Roman reactions to Islam were written by people within the Church - the average Roman probably had very different views. I'll attempt to deconstruct this a bit more later, but the nature of the sources is a big hinderance to any analysis of the seventh century.

The next mention of Arab invaders comes from a faded note written in a Syriac Bible from roughly 637:

. . . Muhammad . . . priest, Mār Elijah . . . and they came . . . and . . . and from . . . strong . . . month . . . and the Romans {fled} . . . And in January {the people} of Emesa received assurances for their lives. Many villages were destroyed through the killing by {the Arabs of} Muhammad and many people were killed. And captives {were taken} from the Galilee to Bēt . . . Those Arabs camped by {Damascus}. We saw . . . everywhere . . . and the {olive oil} that they {had brought} and . . . them. On the twenty-sixth of May, {the sacellarius} went . . . from Emesa. The Romans pursued them . . . On the tenth {of August} . . . the Romans fled from Damascus . . . many, about ten thousand. The following year, the Romans came. On the twentieth of August in the year nine hundred and forty-seven [636 c.e.] there assembled in Gabitha . . . the Romans and many people were killed, from the Romans about fifty thousand . . . In the year nine hundred and forty-{eight} . . .

As you can see, this account did not survive in full and the only concrete information we have from this note is that there was a battle against Arabs led by Muhammad (either in person or this was a reference to the Arabs' reverence of the Prophet; the first option is a tad controversial since traditional Muslim accounts from the late eighth century agree that Muhammad had died in 632), and that then the Romans fought and lost a major battle at Gabitha. Still, the fact that it was written on a blank page in front of a Bible suggest that the writer (probably a monk) was noting down the momentous events he had just witnessed, so it is at least a genuine voice from a Roman eyewitness, which makes this a unique and very important source.

The next sources comes from another anonymous Syriac writer, in a work now known as the Chronicle to 640, written in or soon after 640:

In the year 945 [634 c.e.], the seventh indiction, on Friday, February the fourth, at the ninth hour, there was a battle between the Romans and the Arabs of Muhammad in Palestine, twelve miles east of Gaza. The Romans fled. They abandoned the patrician Bryrdn, and the Arabs killed him. About four thousand poor villagers from Palestine—Christians, Jews, and Samaritans— were killed, and the Arabs destroyed the whole region.

In the year 947 [635/36 c.e.], the ninth indiction, the Arabs invaded all Syria and went down to Persia and conquered it. They ascended the mountain of Mardin, and the Arabs killed many monks in Qedar and Bnātā. The blessed Simon, the doorkeeper of Qedar, the brother of Thomas the priest, died there.

END OF PART ONE